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User manual - z-Tree

1. If the condition is FALSE nothing is done in the first case and in the second case the instructions in the false_statements are carried out Example if type FIRM Prorit v WwW othersProfit w O else type WORKER Bonesi Wy Gi othersProfit v e w You may also carry out conditional calculations by using the if function However carrying out many calculations in this way requires constant repetition of the condition This is inefficient and can become confusing Page 67 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Definition of Treatments z Tree 3 5 More programming if loops and arrays Tutorial The if statement makes it possible to calculate a variable for some records and not for others This can result in undefined cells It is a good practice to initialize variables at the beginning of the treatment Consider a situation where you have 4 types of players and for the different types you have different profit functions You can program this with a nested if statement as follows ie type 1 Meese Galician om else ie tye 2 second calculation else it itype J third calculation else fourth calculation It is not easy to keep track of all the necessary closing brackets With elsif there is an easier way to express the above program there is only one e
2. University of Wy e UZH THURGAU INSTITUTE Zurich OF ECONOMICS at the University of Konstanz Department of Economics z Tree 3 5 Tutorial and Reference Manual Urs Fischbacher Thurgau Institute of Economics at the University of Konstanz Katharine Bendrick Southern Connecticut State University Stefan Schmid University of Zurich Table of Contents z Tree 3 5 Table of Contents Tutorial 1 1 About z Tree 2 1 1 Styles used in this manual 3 2 Introduction 2 1 Terms 4 2 2 A guided tour of a public goods experiment 2 3 First test of a treatment 10 3 Definition of Treatments 15 3 1 Simple experiments without interaction 15 3 1 1 Data structure and simple programming 15 3 1 2 Comments 18 3 1 3 Simple course of action 18 3 1 4 The Stage tree 20 3 1 5 Data display und data input 20 3 1 6 The Variables Profit and TotalProfit 21 3 1 7 Calculation exercise 22 3 2 Interactive experiments Symmetric games 23 3 2 1 Table functions 23 3 2 2 How programs are evaluated 24 3 2 3 Table functions in other tables 25 3 2 4 The scope operator 25 3 2 5 The do statement 28 3 2 6 Application Restricting a table function to the members of one s own group 28 3 2 7 Basic group matching 29 3 2 8 Summary statistics 29 3 2 9 Example Guessing game 30 3 2 10 Example Rank dependent payment 31 3 3 Symmetric simultaneous games 32 3 3 1 Conditional exe
3. The do statement is of particular importance in an auction environment because we are navigating between multiple tables For all of the examples until now we worked primarily in the subjects table In an auction however there is the subjects table for information specific to people and the contracts table where the market transaction information is stored When a subject presses a button for instance this action may be automatically associated with either the contracts table or the subjects table Most likely though we will need to modify some information in both tables leading to the use of the do statement as seen in the next section 3 6 7 Accepting an offer To make it possible to accept an open offer we only have to add a button to a contract list box As in the contract creation box we have to put a program into the button This program marks the offer as bought and sold As in the contract creation box we can access the own record with the scope operator Therefore we need the statement Buyer Subject With this line the offer automatically disappears from the list of open offers since now Buyer is different from 1 However we are not yet through First we have to delete the offers that are no longer valid i e the open offers of the buyer and seller of this offer After the statement above we put Contracts do if Buyer Buyer amp Seller 1 Seller 2 if Seller Seller amp Buye
4. This statement just counts the number of players in the group Profit N Rank BadRank 2 The relevant rank is the average of the two ranks calculated above The payoff depends on this average rank as calculated in this formula 3 3 Symmetric simultaneous games In the previous chapter all subjects had the same parameters In this chapter we explain how to imple ment different parameters for different subjects There are essentially two ways One way is to calculate Page 32 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Definition of Treatments z Tree 3 5 Symmetric simultaneous games Tutorial the parameters conditionally with if functions and statements The second way is to use the parameter table It is strongly recommended that you stick to one of the methods It makes it easier to read your treatments If you feel comfortable with programming it is perhaps easier not to use the parameter table because in this case you have all the information at the same place The parameter table can be helpful if you conduct experiments with different types of players because matching and type assignment is more obvious in the parameter table than in a program in the stage tree 3 3 1 Conditional execution In z Tree it is possible to execute programs depending on the value of the entries in the database This is done by using conditions Conditions are expressio
5. 114 Page vi University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Table of Contents z Tree 3 5 8 3 8 New Box 115 8 3 9 New Header Box 116 8 3 10 New Standard Box 117 8 3 11 New Calculator Button Box 117 8 3 12 New History Box 117 8 3 13 New Help Box 118 8 3 14 New Container Box 118 8 3 15 New Grid Box 119 8 3 16 New Contract Creation Box 120 8 3 17 New Contract List Box 121 8 3 18 New Contract Grid Box 123 8 3 19 New Message Box 124 8 3 20 New Multimedia Box 124 8 3 21 New Plot Box 125 8 3 22 New Chat Box 126 8 3 23 New Slide Show 127 8 3 24 New On Off Trigger 127 8 3 25 New Button 127 8 3 26 New Checker 128 8 3 27 New Item 129 8 3 28 New Point 132 8 3 29 New Plot Input 133 8 3 30 New Plot Graph 135 8 3 31 New Plot Text 136 8 3 32 New Line 137 8 3 33 New Rect 138 8 3 34 New Pie 139 8 3 35 New Axis 140 8 3 36 Slide sequence 141 8 3 37 New Slide 141 8 3 38 Expand All 141 8 3 39 Stage Tree 141 8 3 40 Parameter Table 141 8 3 41 Check 142 8 3 42 Import Variable Table 142 8 3 43 Show Variable 142 8 3 44 Append Variable 142 8 3 45 Append Text 142 Page vii University of Zurich Department of Economics Thurgau Institute of Economics at the Un
6. Definition of Treatments z Tree 3 5 Interactive experiments Symmetric games Tutorial Note however that not using the scope operator can be dangerous If at some time a variable A had been defined in table tc then the product of the second expression no longer goes back to the variable A in table ta but to the A in table tc Note also that if the prefix tc is omitted in front of the product table function the product is taken over the records in table tb and if the prefix tb is omitted in front of the sum table function the sum is taken over the records in table tb Example Consider the following two tables A Vv B vV 1 3 7 8 4 6 10 11 13 14 Assume the following program is calculated in table ta Which expressions are correct and what are their results X1 sum V X2 th sum V X3 th sum X4 sum V X5 tO SUM N SVIE X6 sum product V X Suu procter SW Ia x swul grocer SRW Ie O go etmi proecktee GAA e Y1 sum A Y2 th sum A Y3 th sum A Y4 sum A Y5 th sum A Y6 sum product A Y Boia jock eI FZ WS Sun Producti C EA OS Sie sim aos Cll tea 25 E Z1 sum B Z2 tb sum B Z3 tb sum B Z4 sum B 75 th SUM B Z6 sum product B f Swm procter 18 J7 is gum procuce Sse JA Z9 ilo swine joxeorclbicic J8 e Solution Z1 and 23 to Z8 are incorrect The result of the other expressions equal Pag
7. In this option field there is also the option and in previous stage s This option has to be set if a subject has to go through a sequence of stages before the next subject may enter the sequence of stages In our example this option is not selected Besides this another possibility is to let the subjects enter a stage according to their rank i e the subject with the lowest rank enters the stage first This way the order is not random anymore To do this we define a variable Priority in the subjects table and the variable for the subjects rank in the globals table 1 We write the following program in the globals table at the beginning of the buyers stage subjects do SubjectR Subject random subjects do SubjectsRank subjects count SubjectR gt SubjectR Priority SubjectsRank 2 And in the subjects table at the beginning of the buyers stage as well we write SubjectR Subject random This way the subject with the lowest rank enters the buyers stage first Now we also need to define the option Start If the subjects are supposed to enter a stage sequentially we have to set the option Start if possible i e that a subject can only enter a stage if the previous subjects have passed through the stage in other words the subject waits his turn As a last specification in the stage dialog we set the option Leave stage after timeout In our example we set it to If no input with
8. You can use an illegal value here only if you redefine the variable in every cell Then you double click the fields in which you wish to change the value In this dialog you first give this cell a name that rep resents the type This makes it easier to manage the parameter table Then you enter the program in which the value is changed For instance Type 1 Itis a good practice in programs to use names instead of numbers whenever this is possible So in the public good game we defined a variable Endowment that kept the value of 20 This makes the program easier to understand and easier to change When we have values that distinguish different types it is reasonable to define variables for the type options in the globals table If we have proposers and responders in an experiment we could define as ROPOSERTYPE 1 ESPONDERTYPE 2 vs Then you can define the type as Type PROPOSERTYPE If types are binary it makes sense to define variables as binary types where 1 expresses TRUE and 0 expresses FALSE In the case of the ultimatum game we could use variables as IsProposer and or IsResponder 3 3 4 Group matching The variable Group determines the group matching This variable is initialized at the beginning of the period when the other standard variables are initialized It is then set to the value in the upper left corner of the cell of the specific parameters You can mo
9. format x y Returns x as a string variable rounded to the precision of y stringtonumber s Converts string s to a number If the string does not represent a number 0 is returned stringtonumber s x Converts string s to a number If the string does not represent a number x is returned String function examples s World E Hello Y Esr 7 Hellion Wormlall enar 65 y fie TAURO ERE T ASCTE Cha racer Seb x code A 65 for the ASCII character set joul jes Hinne Skin Elna eene Wat ONA bie Br ITECA alive USEIN DA foros Wiealinyel alin telat Seane Wali jail lt p Ip 7 ey imoyoleyo ater ad pee pos Cind in ehis stecinou na ON WH Wy Vie ake SESE ienei foo Ue Ae S ic soma l2 Sa Oniye 7 wiles su geringeonimoesr 42 p 7 2 Si N ll 9 1 12 Table functions average x average a x Average of the found numeric values count count a Number of records in the table or number of found records find x find a x The first value of the variable where a is satisfied find s find a s maximum x maximum a x Maximum of the found numeric values median x median a x Median of the found numeric values minimum x minimum a x Minimum of the found numeric values product x product a x Product of the found numeric values regressionslope x y Gradient of a linear regression through the found regressionslope
10. z Tree 3 5 Reference Manual Page 106 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 The Stage Tree Elements What can be contained in stage tree elements messagebox multimediabox slideshowbox slideshowelement slideshowelement slidesequence slide chatbox plotbox plotitem item button plotpoint plotline plotpie jloicscSecic plotaxis plottext plotgraph plotinput sile slidesequence slide plotbox checker program plotitem plotpoint plotline plotpie PALotwSCit plotaxis ploLttext plotgraph plotinput checker program checker program plotitem checker program z Tree 3 5 Reference Manual Page 107 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Menu Commands z Tree 3 5 File Menu Reference Manual 8 Menu Commands 8 1 File Menu 8 1 1 New Treatment A new treatment is created It contains the background and the background screens 8 1 2 New Questionnaire A new questionnaire is created It is completely empty 8 1 3 Open Opens a treatment or a questionnaire A dialog in which the treatments are shown appears In order to open a questionnaire you have to select the questionnaire file type 8 1 4 Close Closes the frontmost window 8 1 5 Save Saves a treatment
11. 3 39 Slider handle calculations 77 3 40 Variable initialization in the chat example 78 3 41 Chat box for the chatters 79 3 42 Chat box for the observer 80 3 43 Input item for a string variable and what appears on the subject s screen 81 3 44 String input as it appears on the client s screen 81 3 45 Output the position where the smiley emoticon was found 82 3 46 String output as it appears on the client s screen 82 3 47 Table dialog 83 3 48 Turn information on and off with the display condition 85 3 49 Display condition example 86 4 1 Layout of questions normal layout left and wide layout right 91 6 1 Lab setup in Zurich 100 7 1 General parameters dialog 103 7 2 Bancruptcy rules dialog 104 8 1 Stage dialog 111 8 2 Table dialog 112 8 3 Program dialog 114 8 4 Common options for boxes 115 8 5 Box placement within remaining box 116 8 6 Header box with period and remaining time displayed on z Leaf 116 Page xii University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 List of Figures z Tree 3 5 8 7 Standard box in the stage tree and how it is presented on z Leaf 117 8 8 Calculator button 117 8 9 History box in the stage tree and how it is presented on z Leaf 118 8 10 Client view of the help box 118 8 11 Container box in the stage tree and how it is presented on z Leaf 118 8 12 Grid box example
12. 50 payment file 89 period 18 Period 34 period parameters 35 pi 156 plot axis dialog 140 plot box 70 dialog 125 plot graph dialog 136 plot input 72 action drag 76 134 action new 73 134 action select 75 134 dialog 133 plot line 72 dialog 137 plot pie 71 dialog 139 plot point 72 dialog 132 plot rect dialog 138 plot text dialog 136 port 96 Page 178 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Index pos 157 posted offer market 63 power 156 product 158 Profit 21 program 16 dialog 114 evaluation 24 programming language 154 public goods experiment 5 Q question 90 dialog 145 question form 89 dialog 145 questionnaire 89 export 108 import 109 new 108 open 108 running 93 save 108 start 149 R random 22 156 randomgauss 156 randompoisson 157 record 15 creation 61 regressionslope 158 relational operator 154 remaining box 43 repeat statement 69 156 RepeatTreatment 86 role parameters 35 round 22 157 rounddown 157 roundup 157 RTF 49 168 ruler 92 dialog 145 S same 29 157 scope operator 26 155 screen layout 20 z Tree 3 5 serial port 174 server 4 server eec 95 99 172 session 4 conducting 94 sin 157 slide dialog 141 slide sequence dialog 141 slide show dialog 127 specific parameters 35 sqrt 157 s
13. B summary o amp contracts Event Modifiers amp session Left click Cancel logfile Right click I Shift gt x gue seh a C Key T Alt I Leave Stage when done elected 0 Active screen nosena m Use if a Mouse leaves B Waitingscreen iB Stage 30 Active screen 100 100 x 100 100 C New Select C Drag O 0 50 x 0 50 3 select Select 9 subjects do Selected 1 Selected Action x variable E Standard ok y variable E waitingscreen Figure 3 37 Plot input of the example for action select Action Drag The last example is the drag option To illustrate the drag function we will program a scrollbar We will program a scrollbar in order to show how restrictions can be implemented in this case that the object can only be moved along the x dimension and not the y dimension First we will set some variable values to define the scrollbar limits as well as the scrollbar size and the initial location of the scrollbar In a new program in the background set the left bound to 75 and the right bound to 75 called Left Bound and Right Bound in our example Next set the initial x location to 0 and the rectangle height and width to 10 and 10 respectively Do this in the Background too since we will need to refer to these values as variables later on You can see these programs in Figure 3 38 Slider example Next insert a plot box in the Active screen of a
14. Radiobuttons A radio button is created for every line in the field options These buttons are arranged vertically one on top of the other Slider Scrollbar The slider and scrollbar make a quasicontinuous entry possible Minimum maximum and resolution need to be entered In the wide layout a label can be placed at the margins These labels are entered in the field options The maximum is always the value at the right border the minimum is the value at the left border Maximum may therefore be smaller than minimum Radioline A radio button appears for all possible answers determined by minimum maximum and resol ution In the wide layout a label can be placed at the margins These labels are entered in the field Options The middle button can be separated from the others by entering a number greater than zero for Distance of central button The maximum is always the value at the right most button the minimum is the value at the left most button Maximum may therefore be smaller than minimum Radiolinelabel Label line for radio button lines Labels can be placed above the buttons at the margins The texts for this action are in the Options field Checkbox A checkbox is created for every line in the Options field These checkboxes are arranged vertically one on top of the other The resulting value is a list of all options checked Wide In the wide layout the entry region for the question appears under the label over the whole width and does not
15. The other options in this dialog will be explained later The default options are a good choice Name pK OK No record created or selected Cancel I Clear entry after OK Leave Stage C Yes C No Normal ie stage is not left after click if stage is left after timeout and button is contained in contract creation or selection box Color Automatic C Gray C Red Event time Figure 2 8 Button dialog This completes the first stage In our treatment there is a second stage the profit display stage We select the Contribution Entry stage and choose Treatment gt New Stage In the dialog we name this new stage Profit Display In this Profit Display stage we display the income of the subjects Before we can do this we have to cal culate it We insert a program at the beginning of this stage It is executed for every subject when he enters this stage To insert the program we select the Profit Display stage and choose Treatment New Program In the Program field we enter SumC sum same Group Contribution N count same Group Profit Endowment Contribution EfficiencyFactor SumC N In the first line we calculate the sum of the contributions in the group of the subject Group is a predefined variable It is 1 for the first group 2 for the second group etc It will be explained in detail in Chapter 3 Definition of Treatments In the second line we count the number of su
16. enter the following line into a program of the session table Income TotalProfit How you retrieve data from the session table You can access variables in the session table as in any other table There is only one problem z Tree always checks that you do not use variables that are not defined earlier in the treatment Therefore you have to declare what variables in the session table you will use in a treatment The clean way is to define the variables at the beginning of the treatment within the session table definition All tables are listed at the beginning in the Background of the treatment To define the variables you need to use in a treatment you double click the session table icon and enter the variables into the field Used variables A hack solution consists of defining the variable using an assign ment statement In order not to overwrite the data you do the assignment in a statement that is not ex ecuted ie auem 4 assign VariableYouWantToUse 0 You can also use user defined tables to store the data and reuse it in another treatment If you use variables in the session table it is usually optimal to do it with a program in the session table In this case you can access the corresponding record in the subjects table using the scope operator 3 13 Complex move structures 3 13 1 The start if option It is possible to implement any kind of move structure in z Tree For more complex move structures use the star
17. local directory This way you can run several clients on one PC If the file name eec does not exist the host name of the PC is used The host name is entered in the network control panel under TCP IP 5 7 During a session In the windows opened with Run gt globals Table Run subjects Table Run gt contracts Table and Run summary Table the content of the given table is displayed In these tables the sizes of lines and columns can be changed These tables are automatically exported to the xls file 5 8 Concluding a session Each session ends with a questionnaire Generally the address is asked first so that the payment file can be written Next additional questionnaires are inserted and finally a good bye screen appears which also displays the profit How questionnaires are made is explained in chapter Chapter 4 Questionnaires 5 9 Dealing with a crashed or blocked subject PC All data is stored in various files in readable form as soon as it is complete Besides this all messages exchanged between server and clients are stored in a non text file the GameSafe With the help of these files it is generally possible to continue the experiment after a computer crashes In the case of a problem on a subject PC you proceed as follows If the PC is still working it can simply be restarted It is then automatically reset to the same state it would have been in had the crash not oc curred Of course this also means that it can
18. of 2 If anything else is entered such as I do not know or BoXing then an error message appears that says that only certain values are accepted With the radio option two radio buttons labeled with boxing and with opera are displayed Selecting one of them sets the variable to the corresponding value The following options are available text radio buttons line of radio buttons check box slider horizontal scrollbar and push buttons as shown in the following table All options except the push button option can be used for input items and for output items The push button option can only be used for input items because a push button cannot be displayed differently as selected or unselected How the different options are programmed is explained in the reference manual 3 4 2 Layout in the large Screen design and boxes In experiments subjects work for only one to two hours at the computer They cannot gain much exper ience and should be able to understand screens very quickly For that reason the screen layout of z Tree is rather static The screens are built of fixed rectangular areas called boxes that can be placed freely on the screen Besides the standard box with which you are already familiar there are other boxes for in stance a help box for explanations a header box for information about the current period and remaining decision time and a history box in which you can display information about earlier periods Page 4
19. s lifetime is Period the table is reset whenever the end of a period has been reached i e all records of the table are deleted of course after they have been saved and the table is reconstruc ted from scratch The subjects globals and contracts tables have a period lifetime As in the subjects globals and contracts tables the data that was in a table x in the previous period can be accessed in the table called OLDx Tables with lifetime Treatment are reset after the end of the treatment They do not change after the end of a period Tables with lifetime Session are never reset Nevertheless they are stored at the end of each treatment To be able to access variables defined in a treatment that was executed before you have to declare the variables in the field Used Variables Program execution If subjects do not enter a stage simultaneously programs in a table can be executed whenever a subject enters or only when the first enters the stage or only when the last subject enters the stage You can define the option for your databases The programs in the globals table are executed for the first subject programs in the summary table for the last subject Programs in the subjects and in the session table are executed for each subject who enters the stage 3 12 2 Accessing data from previous periods and treatments If you want to program an auction market you may want the subjects to keep their endowments of money and stock from perio
20. 1 Editing in the stage tree 102 7 1 1 Viewing 102 7 1 2 Adding elements 102 7 1 3 Deleting elements 102 7 1 4 Moving elements 102 7 1 5 Editing elements 102 7 2 The background 102 7 2 1 Bankruptcy rules 104 7 3 Parameter Table 105 7 3 1 Period Parameters 105 7 3 2 Role Parameters 105 7 3 3 Specific Parameters 105 7 4 Screen 105 Page v University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Table of Contents z Tree 3 5 7 5 What can be contained in stage tree elements 105 8 Menu Commands 108 8 1 File Menu 108 8 1 1 New Treatment 108 8 1 2 New Questionnaire 108 8 1 3 Open 108 8 1 4 Close 108 8 1 5 Save 108 8 1 6 Save As 108 8 1 7 Export Treatment 108 8 1 8 Export Questionnaire 108 8 1 9 Export GameSafe 108 8 1 10 Export Table 108 8 1 11 Import 109 8 1 12 Page Setup 109 8 1 13 Print 109 8 1 14 Previous files 109 8 1 15 Quit 109 8 2 Edit Menu 109 8 2 1 Undo 109 8 2 2 Cut 109 8 2 3 Copy 109 8 2 4 Paste 109 8 2 5 Copy groups 109 8 2 6 Paste groups 110 8 2 7 Insert cells 110 8 2 8 Remove cells 110 8 2 9 Find 110 8 2 10 Find Next 110 8 3 Treatment Menu 110 8 3 1 Info 110 8 3 2 New Stage 110 8 3 3 New Table 112 8 3 4 New Table Loader 113 8 3 5 New Table Dumper 113 8 3 6 New Program 114 8 3 7 New External Program
21. 2015 Definition of Treatments z Tree 3 5 Introduction to graphics Tutorial array Rvalue 4 array Cost 4 And then you write the values for each index In our example RValue 1 400 RValue 2 300 RValue 3 200 RValue 4 200 Cost i 20 Cost 2 120 Cost 3 220 Cost 4 220 Then you need to define the index of a trade to assign the corresponding values for the costs and the redemption values NumTrades 0 If NumTrades is set to 0 the first index of the variables redemption values or costs is taken to assign the corresponding values and to run the programs in the stages If it is set to 1 the second value is taken and so on This means that the costs and the redemption values depend on the values that are already traded 3 10 Introduction to graphics 3 10 1 Graphic display In this section we will create an on screen image a smiley face To display graphics in z Tree you use a plot box The plot box sets up a coordinate system so that you can position different types of shapes and other elements on the screen A zal i aan Figure 3 28 An on screen smiley face Page 70 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Definition of Treatments z Tree 3 5 Introduction to graphics Tutorial Plot Box Name OoOo o y V with Frame Distance to the margin p Adjustment of the remaining box Widt
22. 2015 Menu Commands z Tree 3 5 Questionnaire Menu Reference Manual texts in the optional fields are left empty the corresponding question does not appear on the clients screens If the fields First Name and Last Name are left empty then no form appears The payment file is written whenever the last subject has completed or passed through without completing the address form Additional variables from the session table are added to the address form if questions are placed into the address form 8 4 3 New Question Form Question forms consist of a list of questions The layout of the question is adjusted with rulers All question forms except the last must contain a button Name ID Name of the form The name must be unique within a questionnaire Title Title as it appears on the clients screens Program A program that is conducted in the session table for the subject who enters this questionnaire If the variable Participate is set to zero the questionnaire can be omitted 8 4 4 New Ruler Rulers are used to set the regions where labels and questions are positioned Distance to left margin The position can be given in points or in percentage of the screen width Distance to right margin The position can be given in points or in percentage of the screen width Distance between label and item This is the horizontal distance between the label and the question Half of this distance is also kept to the left and right margins Si
23. A label row contains the labels If the table is too long a scrollbar appears The current period appears at the end of the table The scrollbar is adjusted in such a way as to make this line visible at the beginning Page 117 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Menu Commands z Tree 3 5 Treatment Menu Reference Manual 6 History 2D Period OUT Period E0 A OUT a E0 B OUT b Figure 8 9 History box in the stage tree and how it is presented on z Leaf Show also current period If checked all periods including the current period are shown If it is not checked only the previous periods are shown 8 3 13 New Help Box Creates a help box A help box is a box with a label that contains a text A label and a help text can be entered If the help text is too long to appear in the area reserved for the help box a scrollbar appears Figure 8 10 Client view of the help box 8 3 14 New Container Box Creates a container box i e a box which may contain other boxes If you want to directly place the boxes in the figure above it becomes necessary to choose the appropriate sizes By defining container boxes you can easily make sure that the boxes always match one another Container boxes are boxes that can contain other boxes E Active screen Container 12 Container 34 ER Standard 3 E Standard 4 Figure 8 11 Containe
24. A starter on how to prepare the data is given in Section 5 13 Data analysis gsft GameSafe in binary form It can be exported into a readable file but this file will be gigantic The starting time of the session is used as file name The format is YYMMDD_HHMM YY means year MM month DD day HH hour and MM minutes In this way the start of the session can easily be repro duced 5 13 Data analysis The xls file can easily be used for data analysis and there are tools in the Tools gt menu that facilitate this process considerably These commands allow you to separate the different tables into separate files and to merge similar files into a big file for analysis The best way to do this is to copy all the data files into a new directory gt then apply menu Tools Separate Tables to all files You can select all files in one dialog by holding the Ctrl key when clicking Then you apply the Tools Join Files command A dialog appears and in it you add all files which have a similar structure for instance all subjects tables It is not necessary that all merged tables have the same variables The merge tool creates a new table that contains all variables that appear in any of the tables Page 98 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Installation z Tree 3 5 A simple installation with a file server Tutorial 6 Installation 6 1 A simple install
25. CONT er OS payment 10 switching off of machines 11 data analysis While conducting an experiment we mainly work with the menu Run The order of commands in the run menu corresponds on the whole with the course of the session 5 2 Preparation of treatments and questionnaires Before the session begins all treatments and questionnaires in z Tree are defined and saved on the file server How you define treatments and questionnaires is explained in Chapter 3 Definition of Treatments and Chapter 4 Questionnaires Treatments are different for different numbers of subjects Hence in case you are not sure whether all subjects will show up you would like to have the possibility of running a session with varying numbers of subjects depending on how many show up In simple cases the number of subjects which is fixed in every treatment can be changed at the beginning of the session i e before the start of the first treatment In cases where changing the number of subjects involves more than simply changing this number you have the option of preparing treatments for different numbers of subjects We recommend that you make a list of the treatments and questionnaires It should include the names of all of the treatment files for all possible numbers of subjects Alternatively you may list how the treatment files are to be adjusted for all possible numbers of subjects It is a good practice to number the treatments e g Ol_welcome ztt 02_PG
26. Common options for boxes Name Name of the box Used for documentation only With frame Whether there is a frame around the box or not Width Width of the remaining box in pixels p or percent optional Height Height of the remaining box in pixels or in percent optional Distance to the margin Indicates how far away the margin is from the margin of the remaining box in pixels or in percent of the remaining box optional Adjustment of the remaining box Where is the remaining box cut off if at all Page 115 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Menu Commands z Tree 3 5 Treatment Menu Reference Manual te _R_ L Lz 4 lq __R_ a WwW BP L gt a wW gt L gt a gt a W rare Figure 8 5 Box placement within remaining box Width height and distance to the margin are optional Depending on which fields have been filled the box is placed within the remaining box Figure 8 5 Box placement within remaining box shows all cases for the fields width W distance to left margin L and distance to right margin R Display condition If this field is nonempty the box will only be shown if this condition is satisfied The condition is calculated in the subjects table It is reevaluated whenever data is changed i e this condition can be used to turn on and off boxes dynamically If the field is empty the box will always
27. Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Definition of Treatments z Tree 3 5 Interactive experiments Symmetric games Tutorial If you conduct the above program for the summary table then in each period the variable AvProfit is calculated and in the summary table we can view at the average profits made in the treatment 3 2 9 Example Guessing game The experiment The subjects have to enter a number between 0 and 100 The subject who is closest to of the average of all numbers entered wins a prize of 50 points If there is a tie the prize is shared equally among the winners The solution a B profit display 30 globals Xd subjects do amp subjects GroupAverage average same Group Guess amp summary TargetV alue GroupAverage Factor amp contracts Diff abs Guess Target alue session GS subjects do a a globals do BestDiff minimum same Group Diff MinGuess 0 IsWinner if Diff BestDiff 1 0 MaxGuess 100 X amp subjects do IncGuess 0 001 NumWinners sum same Group IsWinner Factor 2 3 Profit Prize IsWinner NumWinners Prize 50 a Active screen i Active screen Standard E Header ED Your Guess OUT Guess a waitingscreen ii 3 Text ED Average guesses OUT GroupAverage ED Please wait until the experiment ED Number to guess 2 3 average OUT Target al
28. Expressions according to which sorting is carried out separated by semi colons When sorting is to be undertaken in descending order the expression is preceded by a minus sign Display Condition Whether the whole slide sequence is shown or not Repeated If the slide sequence should be repeated then add a value larger than 0 The sequence is shown 1 this number times 8 3 37 New Slide Defines a single slide The slide can contain plot boxes Name Name of the slide Display Condition Whether the slide is shown or not Duration How long is the slide shown i e when the next slide is started to be displayed 8 3 38 Expand All Shows all elements by expanding any nested elements i e elements contained within other elements 8 3 39 Stage Tree Opens the window with the stage tree This menu is only active when the parameter table window is in front 8 3 40 Parameter Table Opens the window with the stage tree This menu is only active when the stage tree window is in front Page 141 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Menu Commands z Tree 3 5 Treatment Menu Reference Manual 8 3 41 Check Checks the programs and parameters for errors 8 3 42 Import Variable Table You give the name v of a variable and choose a text file that contains a table Then the line Vio Wi is added into the program of the specific parameters Here w sta
29. J do not draw lines to center fill color frgb 1 00 1 00 0 00 Display condition Figure 3 30 Plot pie Smiley s face Page 71 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Definition of Treatments z Tree 3 5 Introduction to graphics Tutorial Next insert two points Increase the Number of vertices so that the eye appears as a circle rather than a polygon stars are also possible Figure 3 31 Plot point Smiley s right eye shows the location of the right eye the left eye should be identical but located at the point 20 20 Plot Point Size Num vertices Start at angle from x Line color frab 0 0 0 Line width fC Fill color tgb 0 00 0 00 0 00 Display condition Figure 3 31 Plot point Smiley s right eye The next item to insert is a line The first line to insert is shown in Figure 3 32 Plot line Smiley s mouth middle part and is the bottom of the mouth Two additional lines going from the point 20 30 to 30 20 and from point 20 30 to 30 20 complete the mouth Plot Line arrow size arrow width Arrow is closed line color tgb 0 00 0 00 0 00 line width 10 Display condition Figure 3 32 Plot line Smiley s mouth middle part Your smiley is now finished 3 10 2 Interactive graphics In this section we will go through several examples to learn how t
30. Palan Martin Strobel and Jean Robert Tyran We would also like to thank Silvana Christ Alan Durell Armin Falk Christina Fong Cornelia Schnyder Omar Solanki and Beatrice Zanella for helping to present the program in this manual Omar Solanki translated the first German manual into English Page 2 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 About z Tree z Tree 3 5 Styles used in this manual Tutorial 1 1 Styles used in this manual Programs and code snippets are presented in a monospaced font Text that should be replaced with user supplied values or by values determined by the context is shown slanted wE Comelec statements else statements In the example above if else and the parentheses have to be written exactly as shown condition and statements have to be replaced by the appropriate text Labels in dialogs are presented in the text in a sans serif font on a gray background Number of subjects Entries into fields are shown in a box 0 1 Menus and menu commands look like File Save As Keys on the keyboard appear like Enter or Ctrl c Stage tree elements are written in a sans serif font Active screen Page 3 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Introduction z Tree 3 5 Terms Tutorial 2 Introduction 2 1 Terms In anon com
31. Stage tree of the battle of the sexes game 38 3 11 Parameter table of the battle of the sexes game 38 3 12 Stage tree of a private value second price auction 40 3 13 Placement of the box is defined in the box dialog 43 3 14 Box placement 43 3 15 Box placement example 44 3 16 Example of the definition and the resulting layout of a standard box 45 3 17 Grid box examples with column by column or row by row layout 45 3 18 Header box example 45 3 19 Help box example 46 3 20 History box example 46 3 21 Container box example 47 Page xi University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 List of Figures z Tree 3 5 3 22 Calculator button box example 47 3 23 Button placement example 48 3 24 Example of a two stage sequential game 52 3 25 Example of an ultimatum game 53 3 26 Sketch of box arrangement for an auction 56 3 27 Checker dialog 59 3 28 An on screen smiley face 70 3 29 The canvas for a smiley face 71 3 30 Plot pie Smiley s face 71 3 31 Plot point Smiley s right eye 72 3 32 Plot line Smiley s mouth middle part 72 3 33 Smiley s left eye 73 3 34 Record mouse clicks with plot input 74 3 35 Stage tree of the example for action new 74 3 36 Plot rect of the example for action select 75 3 37 Plot input of the example for action select 76 3 38 Slider example 77
32. Start a treatment the order of the clients is fixed The clients table has three columns client Name of the client In general this is the name of the subject PC If a client is no longer connected its name appears in brackets If a client with the same name should reconnect it can continue at the same place where the previous subject left off The caption to the clients table gives the number of clients currently connected state The state in which the subject is at the time Example Ready when the subject is waiting for the next treatment or for the next questionnaire time Displays the remaining time as it is shown to the subjects 5 5 How a client establishes a connection with the server A session begins when the experimenter starts the server program z Tree on the experimenter PC After this the client program z Leaf is started up on the subject PCs z Leaf establishes contact with z Tree on the experimenter PC The communication between z Tree and z Leaf is based on TCP IP 5 5 1 How does the client know the server s address z Leaf can determine the server s IP address with the command line option server ipaddress If for instance z Leaf is started with the command zleaf exe server 100 20 10 233 then z Tree must run on a PC with the IP address 100 20 10 233 This method is very useful if you want to run an experiment without a file server If z Tree is located on a file server however there is a mor
33. The array instruction can have the following forms array arrayvar defines an array with indices from 1 to number of subjects array arrayvar n defines an array with indices from 1 to n array arrayvar x y defines an array with indices from x to y x y a defines an array with indices from x to y fi Wien ars tance d GUSTIN AFETIVA The access to array elements is carried out with arrayvar indexvalue The expression indexvalue is rounded to the nearest possible index and the corresponding value in the array is fetched or filled Example erray OLL0 20 Sls Li ehe Iinges Set Ts lO 15720 PAJ ie pills 5 p20 2 POL 37 ii BEES O20 eo S x plio pl20 Wl sede amp The example introduced at the beginning of this section would now look like this Page 87 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Definition of Treatments z Tree 3 5 Complex move structures Tutorial array b 10 within a background program Hie Joslin B2 eisiel ar ntered by the subject a find type A a Digit alos Isfal F Page 88 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Questionnaires z Tree 3 5 Overview Tutorial 4 Questionnaires 4 1 Overview Each session ends with a questionnaire Generally name and address ar
34. To save this information you can include a program under the plot input to add a record to the contracts table or a custom table every time a subject clicks on the screen d Eon 1B Stage 30 globals Active screen amp subjects 100 100 x 100 100 amp summary 4 new subjects LeftEyex LeftEyey amp contracts X subjects do amp session Click Click 1 amp logfile 94 subjects do contracts new LeftEyex 20 LeftEyeY 20 Owner Subject Click 0 X LefiEyex Active screen Y Left yey waitingscreen ClickNumber Click A 0 0 50 50 0 360 o LeftEyex LeftEyeyY o 20 20 A 20 30 gt 20 30 A 20 30 gt 30 20 A 20 30 gt 30 20 3E Standard OK E waitingscreen Figure 3 35 Stage tree of the example for action new Page 74 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Definition of Treatments z Tree 3 5 Introduction to graphics Tutorial Action Select As an example for the usage of the option Select we will program a treatment in which clicking on a rectangle triggers a program which changes the color of the rectangle In the Background see Figure 3 36 Plot rect of the example for action select introduce a variable called Selected to manipulate the color of the rectangle As in the smiley example we will need a plot box In the plot box we will select the graphic Treat
35. a x y points x y stddev x stddev a x Standard deviation of the found numeric values sum x sum a x Sum of the found numeric values 9 1 13 Iterator iterator v Creates a small table with the variable v Page 158 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Programming Environment z Tree 3 5 Programming language Reference Manual iterator v x Runs from 1 to x iterator v x y Runs from x to y in steps of 1 iterator v X yY Z Runs from x to y in steps of z See also Section 3 9 2 Loops while repeat and iterator in the tutorial 9 1 14 Syntax diagram of the programming language The following syntax description is intended to serve as a reference to experts Syntax used to express the grammar a b a can be replaced by b ab a followed by b alb aorb mx exactly that text a zero one or more repetitions of a a a vse the character x Definitions chigaltils sg Fall Pay Psy Pay ee ee p ge Uieye ee digit09 0 digit19 letter _ rat poot eked ares as auc dal ashe ieee T ToL se pres e ere A ca eae pura ea serene cade lt 0 we ailiaa na sage 0 Mom AAO ae ans cam asa ie pace ag Bae a Rol c saa nc halle ea pars Rete OnE Sve ea RN Gall ceva ee RA imceger s ciigitlS choirt os J TOV wee lcliigauic g imtecer ta chigntOS uot chlemirOs chigalic s p ceal 9 realcigirt
36. a Timeout of 30 seconds This means that the stage is terminated and the Page 64 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Definition of Treatments z Tree 3 5 Clock auctions and deferred actions Tutorial new stage started whenever the time of 30 seconds has expired regardless of whether there is an input or not We have now programmed a posted offer market and finish the treatment by displaying the profits made by sellers and buyers 3 8 Clock auctions and deferred actions 3 8 1 The Dutch auction Ina Dutch auction when a good is sold there is a clock showing a price This price decreases with time As soon as one person decides to accept she gets the product at the current price To implement this institution in z Tree we need a flexible clock We must be able to define the steps of the price decrease as well as the time interval between price decreases This can be done with a later statement If you start with a price of 1000 and every 3 seconds you want to decrease the price by 10 you write the following program for instance in the globals table Price 1000 later 3 repeat iieslcs Ierice nio The later statement has the following general form later expression repeat statements 1 The expression is evaluated Let t be the value of the expression 2 Iftis smaller than zero nothing more happens 3 Iftis at least 0 then af
37. accordingly 3 13 2 Turn information on and off Boxes can be shown and hidden dynamically There is a display condition option in the box A box is shown if the condition is empty or if it equals TRUE Whenever data changes z Leaf checks whether a box must be shown or hidden You can use this feature for instance to control the access to information Below is an example what a subject could see using this option A subject clicks the button Show in structions and the reminder message on the right is shown To return to the decision screen a subject clicks Return to decision a You can transfer or not If you do not transfer you and Please make your input here No transfer the other player will receive 5 points If you transfer 20 points are available The other player can decide whether to keep the money or to distribute it equally between you which means that you both get 10 points Figure 3 48 Turn information on and off with the display condition The two grey buttons include programs which switch a variable between one and zero This variable is used in the box display condition to control whether the information box is shown Figure 3 49 Display condition example shows the stage tree of the example In the decision box the display condition is ShowInfo 0 and in the instruction box the conditionis ShowInfo 1 The variable showInfo is modified when a subject clicks on one of the grey
38. are placed with three different option combinations Page 47 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Definition of Treatments z Tree 3 5 Screen layout rete Buttons Position Arrangement ses Intows sss C Incolumns 2s Buttons Position m Arrangement se 9 C Intows s s In columns vo Buttons Position Arrangement so e C Inrows v se Incolumns so o Figure 3 23 Button placement example If you want to leave space in the size of a button without displaying a button then use an underscore character _ as the name of the button 3 4 6 Background layout On every screen the boxes in the Background are automatically placed first For each screen you can determine whether you want to use these background screens You find the corresponding option Background screen is being used in the screen dialog If this field is checked then the windows of the background are placed first 3 4 7 Insertion of variables into the text Variables can also be inserted in the label and in the layout field of items as well as in help and message boxes Thanks to this you can for instance display a formula with the values inserted Assume that we want to write income 23 5 points where 23 5 is the value of the variable Profit So that the variable does not stand alone on the right hand side it needs to be in
39. be further than before If in the meantime the time set for a stage has passed then the treatment moves ahead by a stage even if not all the clients are connected There are several possible reasons why a subject PC may not resume a treatment It is possible that the server is very busy In this case you simply have to wait a little However if the server is in a wrong state due to a programming error the server has to be restarted If the subject PC is not functioning you can start a new PC As soon as the new client appears it can be manually assigned to the subject who was working on the old computer To do so you select the client field of the new client in the clients table and move it over the field of the old client Page 96 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Conducting a Session z Tree 3 5 What to do if the experimenter PC crashes Tutorial 5 10 What to do if the experimenter PC crashes After a crash of z Tree you have to do the following 1 Restart z Tree Open the clients table 3 Restart all clients with the Run Restart All Clients If some clients do not connect go to the client and reconnect the client manually To reconnect a client manually you quit z Leaf with Alt F4 and start z Leaf again If no client connects then you have four possibilities You can restart all clients manually You can wait a while and t
40. be shown 8 3 9 New Header Box Creates a header box Period i ih tu 4 Remaining time 5 Figure 8 6 Header box with period and remaining time displayed on z Leaf Period number and time are displayed in a header box The following options can be adjusted Show current period number Period number is displayed or not Show total number of periods Total number of periods is displayed or not Name of Period Name in front of the period number Period is used as standard However Trading day or Round for example are also possible Term for out of At 3 out of 10 Periods Prefix for trial periods Trial is standard Display time Is the time being displayed to the subjects If not not even a time message is generated Term for Remaining time Remaining time sec is standard If this field is empty no time is displayed In this way you can do without displaying the time and yet ask the subjects to continue when time has run out Page 116 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Menu Commands z Tree 3 5 Treatment Menu Reference Manual Term for Please reach a decision Text that appears when the allotted time has run out Please reach a decision is standard 8 3 10 New Standard Box Creates a standard box 6 Standard E0 text as headline a0 E0 shows variable a OUT a E0 shows variable b OUT b shows va
41. buttons Buttons no longer conclude the stage So subjects can make an indefinite number of entries We need a table without predefined number of records An example is the contracts table It contains an indefinite number of records In the contracts table we store the subjects offers There are new box types the contract creation box the contract list box and the contract grid box These boxes allow subjects to make select view and edit offers By using several boxes it is possible to do different things on one screen in one stage For example subjects can make offers in one box and accept offers in another box Page 54 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Definition of Treatments z Tree 3 5 Continuous Auction Markets Tutorial By placing programs into buttons it is possible for subjects to take different actions based on the same data For example the entry of a price can mean sell for this price or buy for this price In the following sections we go through the development of a simple double auction In this double auction sellers can sell a product that has a cost of zero to them and a value of 100 to the buyers Each subject can trade at most one item We first show how the entries of the subjects are stored in the contracts table Then we show how to make the box for making an offer the box for displaying the offers and the bo
42. define variables When you check the Input checkbox more fields appear in the item dialog In the Minimum and Maximum fields we declare the lower and upper bounds of the value that the subjects may enter In the Layout field we enter the precision of the number If the number entered by a subject is not a multiple of the value entered in the Layout Page 20 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Definition of Treatments z Tree 3 5 Simple experiments without interaction Tutorial field or if the value is not within the declared bounds an error message appears on the subject s screen In Figure 3 4 Input item dialog we show the dialog of an input item This item defines a field on the subjects screens In this field the subjects must enter a number The value of this number must be between 0 and 12 and it must be a multiple of 1 Therefore it is possible to enter 4 8 but it is not possible to enter 2 15 or 4 55 Your decision OK Cancel Variable Decision Layout f1 V Input Minimum Maximum I Show value value of variable or default I Empty allowed Default Event time Figure 3 4 Input item dialog At the end of a standard box we can place a Button element so that a button appears in the standard box on the subjects screens If a subject presses the button it is first checked whether all conditions for the input it
43. else was the winner gt mu ED Your profit OUT Profit OK E waitingscreen Figure 3 12 Stage tree of a private value second price auction The program is shown in Figure 3 12 Stage tree of a private value second price auction In the beginning of the first stage we generate the subjects private values for the good In the stage Bid subjects then enter their bid values The profit calculation in the Profits stage has 5 steps First we calculate poten tialwin to keep track of the subjects who made the highest bid Since it is possible for several people to have the highest bid we allow for the possibility to pick one random winner among all of the highest bidders Next we use winID to give each potential winner a unique ID With winIDwinner in the globals table we select a random number In the third program we find the subject with the winID value equal to the random winIDwinner value and give this subject the value win equal to one Everyone else gets a win value of zero so we have selected our winner Last we must find the price that the winner will pay and calculate her profit The price is the highest price among those who have not won and the Profit for the winner as stated above is equal to the private value minus good s price All other subjects make no profit On the subjects screens we show whether they were a winner or not and what Page 40 University of Zurich Department of Economics Thurgau Institute
44. evaluated in the subjects table If it is TRUE the program is executed by the z Leaf of the corresponding subject There is no error message if the program cannot be started Page 114 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Menu Commands z Tree 3 5 Treatment Menu Reference Manual Run On Defines whether the program is started on the z Tree computer or on z Leaf z Tree The program is started on the z Tree computer z Leaf The program is started on the z Leaf computers for which the condition is satisfied Command line Program name and parameters of the program as if they were entered in a command window Current Directory Directory in which the program is started Be aware that the client computer might have a different file structure than the the z Tree computer 8 3 8 New Box The subjects screens are made up of boxes These are rectangular parts of the screens The boxes are positioned within the remaining box in the order in which they appear in the stage tree At the beginning the remaining box constitutes the whole screen Later the remaining box is adjusted according to the definition of the boxes The dialog for a box is explained below x Name OoOo o IV with Frame Distance to the margin p m Adjustment of the remaining box Width p Cancel Height p I top J left J right T bottom Display condition Figure 8 4
45. examples x iouiacl SAS 67 20 e 77 SHO moume 345 607 O 1 e 7 845 7 v one 2 5 1 jp il y round 2 5 i iF fol Ep Z Z r ounddonn Eko DP A a roundup 3 6 1 be HB N ll 9 1 11 String functions In the following x y and z are numeric expressions and s t and u are string expressions Some characters will be replaced in the output file the quote is replaced by q new line by n tab by t and backslash by char x Returns the character specified by a numeric code x of the used character set x is anumber between 1 and 255 code s Returns a numeric code for the first character in string s The returned code depends on the character set used mid S x y Returns the middle of the string s starting at character num ber x and going for y characters The counting process starts at 1 that is the first character has a place value of 1 pos s t x Returns place number where string t occurs in string s starting the counting process at number x len u Returns the number of characters in string u upper s Returns string s in capital letters Page 157 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Programming Environment z Tree 3 5 Programming language Reference Manual lower s Returns string s in lower case letters trim s Trims the outside spaces around text letters but not spaces within text
46. in the stage tree or in the questionnaire 8 2 4 Paste In the parameter table Copies a table from the clipboard and pastes it at the selected position In the stage tree or in the questionnaire Copies the branch from the clipboard and pastes it at the selected position 8 2 5 Copy groups Copies the groups of the selected area of the parameter table onto the clipboard Page 109 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Menu Commands z Tree 3 5 Treatment Menu Reference Manual 8 2 6 Paste groups Copies the groups from the clipboard and pastes them at the selected position in the parameter table 8 2 7 Insert cells Adds more rows or columns immediately after the last row or column selected If more than one row or column is selected a corresponding number of rows or columns is added 8 2 8 Remove cells Removes complete rows or columns Complete rows are selected by clicking at the small cell at the left border of the parameter table Complete columns are selected by clicking at the cell at the top of the parameter table 8 2 9 Find Not yet implemented 8 2 10 Find Next Not yet implemented 8 3 Treatment Menu 8 3 1 Info Opens a dialog in which the parameters of the selected element can be viewed and changed 8 3 2 New Stage A stage corresponds to a screen that a subject has to go through It actually consists of two screens
47. kind of calculation can be simplified The following expression calculates the sum of all g in the subject s own group Ss sum Group Group g We can read this expression as follows My s is the sum over the g s of those subjects whose Group is equal to my Group In many contexts it is correct to translate the scope operator into my as we did it here However the correct intuition is that the scope operator refers to the my in front of the s The scope operator refers to the record that contains the s we are calculating We need the scope oper ator where we want to access cells in the record belonging to the s we are calculating and not cells in the record belonging to the g in the table function As performing table functions on one s own group is something very common the function same was specially introduced for such calculations The expression same x is an abbreviation of x x The expression above may therefore be written in the following way e sum same Grova i mechs Thanks to this operation the scope operator becomes invisible It is not necessary to understand the scope operator in detail in order to understand a program intuitively However if you want to write your own programs a deeper understanding of the scope operator is crucial 3 2 7 Basic group matching With the menu Treatment gt Matching groups can be set up in partner or stranger designs Partner matching is fixed m
48. language Reference Manual Grammar program statementlist statementlist statement statementlist i statement lvalue expression while boolexpression statementlist repeat statementlist while boolexpression later expression do statementlist vlaterY i Expression MELD MA Vrepeat t ui statement List 1 vdots tatement Gist 9 tabolerdentif irer 9 9 Welol m e uea ement St new statementlist tableidentifier new statementlist if boolexpression statementlist elseclause array arraydeclaration elseclause elsif boolexpression statementlist elseclause else statementlist r lvalue variable arraydcclard tONE a DENI PE Ee IDENTIFIER expression IDENTIFIER expression expression expression expression expression IDENTIFIER expression summand expression expression expression expression expression expression summand factor summand summand summand summand n Page 161 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Programming Environment z Tree 3 5 Programming language Reference Manual reece RENG NUMBER variable expression FUNCTIONN
49. new stage In the plot box should go the three lines and a rectangle One horizontal line should go from the left bound to the right bound and two vertical lines should bound the horizontal one For the rectangle coordinates set x to the variable x and y to zero In the rectangle insert a plot input item and under Action click Drag Several empty fields will appear pO p and p are the points which will define how the plot item will move in relation to the mouse The point p0 is the point where you first click the shape The point p is where the mouse is currently moved and p is where the object should be moved to while dragging This means that the object is moved by p p Note that you have to take into account that the object is not necessarily be picked at the center so we need to keep track of the old center of the object To modify the location of the object when the mouse is released insert a program into the drag input item With these elements we can complete the scrollbar Now we will go into detail about the plot input item and the program within it Page 76 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Definition of Treatments z Tree 3 5 Introduction to graphics Tutorial Background P amp globals Plot input amp subjects N oo summary a contracts 4 session Event Modifiers el logfile Left click EN subject
50. of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Definition of Treatments z Tree 3 5 Screen layout Tutorial E Active screen B E Container 12 E Standard 2 Container 34 E E Standard 3 E E Standard 4 Figure 3 21 Container box example If we move a box from one place to another inside the stage tree it is moved after the box where the mouse button is released By moving a box over the icon of a container box it is moved into the container box and positioned at its beginning Calculator button box Defines a button as shown below which calls the Windows Calculator It serves as a substitute for subjects who have forgotten their calculators Figure 3 22 Calculator button box example 3 4 5 Button placement To confirm input and to conclude a stage you use buttons They can be placed into standard boxes and into grid boxes By default they are placed at the bottom right corner If you prefer another place in the box then you can choose another option for the buttons position in the box dialog If you have more than one button then they are placed in a row at the bottom The necessary amount of rows are created In the box dialog there are two fields where you can modify the button positioning You can define where the first button is placed Position and where the subsequent buttons are positioned Arrangement In Figure 3 23 Button placement example we show how five buttons
51. of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Definition of Treatments z Tree 3 5 Simple experiments without interaction Tutorial A contribution23 ws Buyers_offer BuyersOffer Not allowed as names of variables 12a starts with a number y 2 13 contains spaces Golo contains dots Buyer sOffer contains apostrophe H l ne contains diacritical marks Some variables are predefined i e they appear in every treatment Other variables are specific to a treatment they are defined in programs Programs are placed at the beginning of stages or into the Background between the table definitions and the Active screen Programs are always defined for a par ticular table in other words they are always executed in a particular table This table is declared in the program dialog as shown in Figure 3 2 In the program dialog you have to specify which table the program will run in In this dialog the dropdown menu contains all tables available in the treatment Table Owner Var Table subjects 7 Owner Var globals a Condition Condition jgeyeapen summary contracts Program Po Program session Figure 3 2 In the program dialog you have to specify which table the program will run in subjects The easiest table is the globals table because it contains exactly one record Hence the variable also de termines the cell So we can talk about the value of a globals
52. of Economics at the University of Konstanz 20 2 2015 Definition of Treatments z Tree 3 5 Screen layout Tutorial their profit is Note in this example there are variables inserted into text How to do this will be explained in more detail later 3 3 10 Programming group matching Defining the matching with the menues has the disadvantage that the command has to be reapplied if the number of subjects or periods changes This is for example relevant when you test the treatment with few subjects Since the Group variable is a normal variable you can also define it in a program Below you find examples of partner and stranger matchings If you define the groups in a program you should set the number of groups in the backgroud to 1 in order to avoid an error message NumInGroup X whatever you like N subjects count NumGroups N NumInGroup whatever you like Partner matching 111222333444 subjects do Group roundup Subject NumGroups 1 Partner matching 123412341234 subjects do Group 1 mod Subject 1 NumInGroup Stranger matching repeat subjects do R random subjects do Rank count r gt r while subjects sum Rank N N 1 2 gt 5 repeat in case of ties subjects do Group 1 rounddown Rank 5 NumGroups 1 3 4 Screen layout So far you know how input is made with the help of input items in standard boxes and you know how to display varia
53. open dialog opens To each row of the data file some row of the key file will be added Key File guilabel Path of the key file If you click the label Key File a standard file open dialog opens The key file contains the information to be added to the data file Link variable s comma separated list of variables in the data file Key variable s comma separated list of variables in the key file Output file Path of the output file If you click the label output file a standard save file dialog opens The data file contains one row per row of the data file Each row contains the corresponding row of the data file followed by a row of the key file The row that is taken from the key file is the row in which the key variable has the same entry as the link variable in the data file Example Data file a b c 4 3 7 5 1 8 6 1 9 Key file k a 1 12 2 22 33 Data variable b Key variable k Output file a b e k d 4 3 7 3 33 5 1 8 a1 fa 6 1 9 1 Page 151 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Menu Commands z Tree 3 5 View Menu Reference Manual 8 6 4 Append Files Several files containing tab separated tables with a header called input tables can be merged The output table is a table containing all the records of all the input tab
54. payment file In this way the payment file lists the net amounts paid out to the subjects Another subject takes on the role of the subject released In this case all profits are reset to zero and the new subject is able to continue the experiment at the PC of the released subject The subject drops out You need to be careful about this as it may change group sizes and the inform ation on the active subjects may therefore no longer be correct 5 12 The files generated by the server The following files are created in the course of the experiment They are distinguished by their suffixes All files are tab separated text file The use of the extension xls only allows to open the file directly in Excel Do not open and save your files under the original name Sometimes Excel creates dates out of numbers like 1 2 It is easier to restore the data from the original file In order to avoid the date problem you have to instruct Excel to use the point for decimal numbers and not the comma pay Payment file Name of client computer profit and possibly subject name adr Addresses of the subjects sbj Questionnaire responses Without subjects names xls Contains all tables shown in the course of the session The first column contains the treatment number the second the name of the table and the third column contains the period variable As the tables are stored chronologically you need some preparation to work with them
55. payment file is updated Page 92 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Questionnaires z Tree 3 5 Making individual receipts Tutorial A questionnaire is started with the command Run gt Start Questionnaire This command is located at the place where the command Run gt Start Treatment is located when a treatment window is open While subjects are answering the questionnaires the clients remain in the state questionnaire The window subjects table shows which questionnaire is currently being answered 4 4 Making individual receipts The payment file is a good basis to produce individual receipts using a mail merge program which is contained in most word processors It is a good idea to produce a step by step procedure for your envir onment that is somewhere available in the lab Page 93 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Conducting a Session z Tree 3 5 Quick guide Tutorial 5 Conducting a Session 5 1 Quick guide The running of a session consists of the following steps preparation of treatments and questionnaires startup of the experimenter PC startup of the subject PCs arrival of subjects start of the session and the first treatment observing the course of the session start further treatments conclusion of session with a questionnaire SO GO
56. standard box There is however an easier way of doing this In a contract grid box you can display a part of a contracts table and unlike to the contract list box input variables can be added for each record So you can create a contract grid box that displays the records of the contracts table that correspond to the trades of a subject By adding an input item with a variable Quality the subject can enter a quality to each of the trades 3 6 12 Examples of double auctions In this section we give several examples of auctions with specific programming problems Page 61 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Definition of Treatments z Tree 3 5 Continuous Auction Markets Tutorial Single sided auction Since we have already gone through a double auction we will start with this as a baseline In a single sided continuous and simultaneous auction we will allow certain subjects or certain groups of subjects to do things that other subjects or groups of subjects are not allowed to do To do so we first program an entire double auction i e we program every box that will be passed through by any subject or group of subjects Then we define and implement the conditions that allow only the desired subjects or group of subjects to see a certain box Conceptually let s go through the treatment step by step 1 To allow only one group of traders to post offe
57. that has not pressed the button yet If there is only one subject left we want the whole group to leave the stage because the auction then has ended The corresponding condition is the following Page 66 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Definition of Treatments z Tree 3 5 More programming if loops and arrays Tutorial if count same Group amp Out lt 1 subjects do if same Group LeaveStage 1 The group now leaves the auction stage and enters the result stage in which the subjects are informed about the winner s price and whether they themselves are the winners or not Do not forget to put a checker into the Exit button This checker contains the following condition count same Group amp Out ss 2 If this condition is not satisfied anymore there is only one subject left that has not pressed the Exit button yet This subject has won the clock auction 3 9 More programming if loops and arrays 3 9 1 Conditional execution of statements If you wish to carry out something only under certain conditions you can utilize the if statement It may be utilized in the following forms if condition true_ statements if condition true_ statements else false_ statements The condition is evaluated first If it is TRUE the instructions in the true_statements are carried out
58. the active screen the subject goes through and the waiting screen that is shown when the subject leaves the stage and waits for the next stage In the following we show the stage options Page 110 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Menu Commands z Tree 3 5 Treatment Menu Reference Manual Name Stage m Start Cancel C Wait for all Start if possible Start if m Number of subjects in Stage i I and in previous stagefs m Leave stage after timeout fno input C Yes C No Timeout 30 Figure 8 1 Stage dialog Name Name of the stage Used for documentation and as a name for the state in the clients table Start Wait for all Subject may not enter this stage if not all subjects are at least in the waiting state of the preceding stage Start if possible No condition for subjects to enter this stage Start if A condition can be given that must be satisfied before subjects can enter the stage This condition is calculated in the subjects table Be careful that this condition is eventually satisfied Otherwise the experiment will never continue Number of Subjects in Stage At most one per group in stage If checked only one subject per group can be in this stage This option is used in posted offer markets and in previous stage s If the checkbox is checked this stage and the preceding stage form
59. the Treatment gt Matching menu For every program z Tree checks that no undefined variables are used Variables are defined in input items and when they get assigned a value However assignments in the parameter table are not con sidered definition This means that variables that are only defined in the parameter table are not con sidered as defined in the stage tree so you have to initialize them in a program in the Background of the stage tree This also guarantees that these variables always have a default value even if they are not defined in every cell in the parameter table Values that are assigned in the Background can be overridden in the parameter table because at the beginning of a period the database is set up as follows Setting of standard variables as Period Subject and Group Running of programs in Background Running of subject program in current period in the subjects table Running of role program in subjects table Running of period program in globals table Ss OT He Ge ee Running of programs of first Stage Page 35 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Definition of Treatments z Tree 3 5 Symmetric simultaneous games Tutorial Example Let us suppose that there are different types of subjects e g type 1 and type 2 In this case you first define a default value for the variable in the Background e g Type 0
60. this prefix notation in a program for the subjects table If you do not explicitly specify the table then the current table is used This means that when you execute the program AVX average X in the globals table the average will be calculated in the globals table and the variable X refers to a variable in the globals table For nested expressions the current table is the table in which a variable at the place of the table function would be executed Consider the following program of the globals table Y globals product A subjects average sum B C In this program the product table function does not need the globals prefix and the sum table function is evaluated in the subjects table as the variable C 3 2 4 The scope operator Let us suppose you want to calculate the expression Xi cos A B J It is the same expression as in Section 3 2 1 Table functions except for the fact that we wish to use in every summand of the sum the variable A of the record in which the cell X lies and not the A of the Page 25 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Definition of Treatments z Tree 3 5 Interactive experiments Symmetric games Tutorial record of B In order to express this the variable A must be preceded by a colon This colon is called the scope operator x Sum cos aA B es Let us look at a table with three records i
61. y Natural logarithm of x Base 10 logarithm of x Maximum of x and y Minimum of x and y Remainder after x is divided by y TRUI TRU 3 1415 E if and only if a is not true E if and only if a or bis true x if x is positive If x is negative and y is an odd number or 1 y is an odd number x is returned otherwise x Y is returned Uniformly distributed random number between 0 and 1 Normally distributed random number with average 0 and standard deviation 1 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Programming Environment z Tree 3 5 Programming language Reference Manual randompoisson x Poisson distributed random number with average x the result is a whole number round x y Rounds x to a multiple of y i e supplies the multiple of y that is closest to x rounddown x y Rounds x down to a multiple of y i e it returns the greatest multiple of y that is smaller or equal to x This definition is also employed for negative numbers roundup x y Rounds x up to a multiple of y i e it returns the smallest multiple of y that is greater than or equal to x This definition is also employed for negative numbers same x Short form for x x Therefore this function is only feasible in table functions x may also be an expression sin x Sine of x sqrt x Square root of x Rounding
62. ztt 03_SVO ztt and 04_questionnaire ztq 5 3 Start up of the experimenter PC Switch on the experimenter PC log in and start z Tree If you want to start z Tree with a special option for example with respect to where to store the data use a command file to start z Tree z Tree has a window that displays which clients have started up and established contact This information is displayed in what is called the Clients Table which will be described in more detail in the next section The name under which one logs in depends on the installation Typically one will set up a user account for all persons who carry out experiments Page 94 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Conducting a Session z Tree 3 5 The clients table Tutorial 5 4 The clients table The clients table shows which clients are connected to the server It also contains information about the state of the clients i e which screens are currently being displayed to the clients You may open the clients table with the first command from the Run Menu Each line corresponds to a subject This subject is seated at a PC on which the client is running column Clients As long as no treatment is started the clients can be moved to other lines They can be sorted and shuffled with the commands Run gt Sort Clients and Run gt Shuffle Clients respectively As soon as you
63. 1 3 6 11 Adding good properties 61 3 6 12 Examples of double auctions 61 3 7 Posted offer markets 63 3 7 1 Example for a posted offer market 64 3 8 Clock auctions and deferred actions 65 3 8 1 The Dutch auction 65 3 8 2 Leaving a stage 65 3 8 3 Auction trial periods with simulate data 66 Page iii University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Table of Contents z Tree 3 5 3 8 4 Double auction with an external shock 66 3 8 5 Exit in an ascending clock auction 66 3 9 More programming if loops and arrays 67 3 9 1 Conditional execution of statements 67 3 9 2 Loops while repeat and iterator 68 3 9 3 Example Cost function using arrays 69 3 10 Introduction to graphics 70 3 10 1 Graphic display 70 3 10 2 Interactive graphics 72 3 11 Free form communication Strings and other data types 78 3 11 1 The chat box 78 3 11 2 String operators and functions 81 3 12 Data use across periods and treatments 82 3 12 1 Definition of new tables 82 3 12 2 Accessing data from previous periods and treatments 83 3 12 3 Copying data from treatment to treatment with the session table 84 3 13 Complex move structures 84 3 13 1 The start if option 84 3 13 2 Turn information on and off 85 3 13 3 Moving back 86 3 13 4 Treatments of indefinite length 86 3 13 5 Example Strategy method using ar
64. 1 Concepts In the treatments discussed so far the basic structure was very simple In each stage the players enter their decision confirm the decision with a button and then wait until the experiment can proceed i e they wait until they can proceed to a next stage With this mechanism it is possible to implement any kind of normal form or extensive form game However many economic experiments use market insti tutions that cannot be implemented as games Consider for instance a double auction In this market institution sellers and buyers can make offers These offers are shown to all market participants The buyers can accept the sellers offers and the sellers can accept the buyers offers This institution differs from the treatments we have programmed so far in the following ways The subjects do not make a predetermined number of entries We do not know in advance how many offers will be made We do not know in advance in what order offers are made i e we do not know who will be the next to decide Even subjects who do not make an entry are informed about other players decisions i e all offers are shown to all subjects The auction is automatically terminated after a certain time To deal with continuous auctions we use the following concepts in z Tree In the stage tree dialog there is an option for terminating a stage automatically when the time has expired This also changes the default behavior of
65. 108 gettime 156 graphics 70 interactiv 73 grid box 45 dialog 119 Group 28 36 group matching 36 defined in a program 41 H header box 45 dialog 116 help box 45 dialog 118 history box 46 dialog 117 I if statement 33 155 if 31 156 input item 20 42 Page 177 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Index text entry 81 IP address 95 173 item 20 42 dialog 129 formatting examples 132 formatting option 130 iterator 69 158 L language 99 questionnaire 147 treatment 144 later statement 65 156 leave a stage 66 LeaveStage 66 len 157 In 156 log 156 logical and 155 logical operator 155 logical or 155 logical value 33 loop 68 lower 158 M matching 29 absolute stranger 143 absolute typed stranger 143 as first selected period 142 partner 142 stranger 143 transformation 144 mathematical operator 154 max 156 maximum 158 median 158 message box dialog 124 mid 157 min 156 minimum 158 mod 156 multimedia box dialog 124 multiplication 154 z Tree 3 5 N new statement 61 155 not 156 O or 156 output item 20 42 P parameter table 35 append text 142 append variable 142 copy groups 109 dialog 105 import variable table 142 insert cells 110 paste groups 110 remove cells 110 show variable 142 Participate
66. 2 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Definition of Treatments z Tree 3 5 Screen layout Tutorial In the next sections we first explain how boxes are placed on the screen Then we present some of the specialized boxes 3 4 3 Placing boxes Boxes are positioned one after the other on the screen By defining size and or distance to the margin as shown in Figure 3 13 Placement of the box is defined in the box dialog you can determine where the box appears Any size can be given in screen pixels p or in percent x Name IV with Frame r Distance to the margin p r Adjustment of the remaining box Width p l Cancel Height p E eight p I let z top F tight bottom Figure 3 13 Placement of the box is defined in the box dialog The positioning of boxes is always relative to the so called remaining box At first the remaining box constitutes the whole screen Later the remaining box is adjusted according to the definitions of the boxes For example if you place a header box on the top of the screen and you want to place the rest of the boxes below this header box then you can cut the top away You just have to check the top checkbox of the Adjustment to the remaining box field in the box dialog This means that the bottom of the header box becomes the top of the remaining box Width height and distance to the margi
67. AMEO FUNCTIONNAME1 expression FUNCTIONNAME2 FUNCTIONNAME3 expression expression expression expression expression vif u i poolexpression 1 expression 1 expression tablefunction variable IDENTIFIER arrayvariable SCOPEOPERATOR variable r arrayvariable IDENTIFIER expression tablefunction puretablefunction tableidentifier puretablefunction T puretablefunction TABLEFUNCTIONO TABLEFUNCTIONO boolexpression TABLEFUNCTION1 expression TABLEFUNCTION1 boolexpression expression TABLEFUNCTION2 expression expression TABLEFUNCTION2 boolexpression expression expression tableidentifier IDENTIFIER ITERATOR IDENTIFIER Tvs Y 4 IDNA Y exyoeassaleim V ITERATOR IDENTIFIER expression expression TTERATOR 1 TDENTIFTER pY escOres SloOnmu umC xp mes sommes U7 Gxoreseiom Page 162 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Programming Environment z Tree 3 5 Scope environment Reference Manual boolexpression boolatom boolatom OPBOOL boolexpression r boolatom BOOLFUNCTIONNAMEO expressi
68. Decision 1 If you wish to calculate a condition and keep it for future use you have to store it in a normal variable i e in a number In this case you use the standard 0 for FALSE and 1 for TRUE An alternative to the if function is the if statement There are the following forms iit Comelitiestoia 1 statementsl or Page 33 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Definition of Treatments z Tree 3 5 Symmetric simultaneous games Tutorial Mel Gomore ea h ee statements1 else statements2 If the condition evaluates to TRUE then all of the statements between the first pair of curly brackets are executed statement s1 If it evaluates to FALSE then in the first case nothing happens and in the second case all the statements between the pair of curly brackets after the else statement are executed statements2 An assignment statement using an if function can be translated into an equivalent if statement For instance a ili x Wp is equivalent to aig Ce 4 Ze x else z yi In this example the second form is more complicated However it is better suited in cases where we use one condition in several expressions For instance this is the case when we have different types of players with completely different payoff functions If we have to differentiate between more than two situations then the e
69. Exch rate Fr ECU f1 Lump sum payment ECU Show up fee Fr Bankruptcy rules Start time of the period Compatibility first boxes on top Options T without Autoscope Figure 7 1 General parameters dialog Number of subjects This number is constant for a whole session Therefore all treatments must have the same number of subjects Number of groups Number g of groups to which the subjects are assigned This means that the subjects belong to a group with an ID between 1 and g This value is used for the matching commands and for checking practice periods Number of periods in which no profit is paid out The number entered can be negative In this case the period counter starts later If for instance the number of trial periods is 2 and the number of paying periods is 10 then the treatment extends from period 3 to period 10 paying periods Number of periods in which the profit is paid out Exch rate Fr ECU How many Francs are paid out per experimental currency unit Lump sum payment ECU Amount in internal units that is credited at the beginning of period 1 of the treatment This amount figures in the variable TotalProfit Show up fee Fr Amount credited to the subjects at the start of the session Only the show up fee of the first treatment played is decisive Bankruptcy rules By clicking this button the parameter of the bankruptcy rules may be adjusted In the tutorial you g
70. If more than one button is defined in this box the buttons can be placed either in rows or in columns If they are placed in rows z Tree first tries to fill a row starting from the corner given by the button position If the first row is full a next row is filled starting from the same corner 8 3 16 New Contract Creation Box Creates a contract creation box We show in an example how a subject can enter two new contracts in a contract creation box A contract should contain the values x y and z Therefore we put three input items x y and z as well as an OK button into the contract creation box Figure 8 13 Contract creation box in the stage tree shows how the contract creation box looks like in the stage tree B E Contract creation box ED X IN x E0 Y IN y OZ IN z OK Figure 8 13 Contract creation box in the stage tree How the contract creation box looks in z Leaf can be modified in the box s dialog Table contracts Num records f1 Records display Empty records allowed C Labels on the top 7 Allrecords empty allowed Labels on the left Buttons Pasition Arrangement 2 12 38 Inrows 2 os In columns o o Figure 8 14 Contract creation box records arranged with label s at the left hand side Table contracts v Num records f1 Records display Labels on the top C Labels on the left Empty records allowed T Allrecords empty allowed Buttons Position Arrangement
71. Oo Inrows CO In columns C CO R Figure 8 15 Contract creation box records arranged with label s on top Page 120 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Menu Commands z Tree 3 5 Treatment Menu Reference Manual When you click the button z Tree checks if all entries have been made Next the checkers in the button are checked and if they are OK two new contracts are added to the contracts table Finally the programs of the button are run If we are in an auction stage further entries can be made otherwise the stage is concluded You may specify the following options Table All contract boxes can be linked to any user defined tables Num records Number of records that have to be entered Only one record is feasible in an auction stage You can also enter a variable from the subjects table here for example a constant numContracts In this way you can define treatments in which subjects have to enter different numbers of contracts Records display The records can be displayed in columns or in rows In the first case the labels appear on the left hand side in the latter case on top of the input fields Figure 8 14 Contract creation box records arranged with label s at the left hand side and Figure 8 15 Contract creation box records arranged with label s on top illustrate the two options Empty records allowed If this option i
72. TMOVERTYPE 1 0 H E Active screen E Waitingscreen 2 second mover a subjects do Participate iff Type SECONDMOVERTYPE 1 0 E Active screen E Waitingscreen Figure 3 24 Example of a two stage sequential game 3 5 3 Ending a stage For each stage the time available to the subjects is fixed in the Timeout field The expression entered is calculated in the globals table If different stages should have the same time out times define a variable in the globals table and enter the name of this variable in the time out field After the time set for a stage has run out the continuation of the game depends on the option set in the stage The default behavior depends on whether entries have to be made in this stage or not If the subject does not have to make any entries on this screen then the stage ends when the time set for the stage has run out i e the subject arrives at the waiting state of the stage and may go on from there If entries have to be made the time displayed is simply a guideline When the time has run out a message saying Please make your decision now appears However the game does not continue until the entries are made If no timeout should occur you can enter a negative number The subjects will then have an unlimited amount of time at their disposal If the time out is set to zero then the subjects will arrive at the waitingscreen straight away If you do not want to leave a stage aut
73. The label is only displayed if the item does not contain a variable The individual options are Num rows Number of rows of the grid including label row if it exists Num columns Number of columns of the grid including label column if it exists Input row by row The items are filled into the grid row by row By pressing the tab key the subject can make the entry row by row Input column by column The items are filled into the grid column by column By pressing the tab key the subject can make the entry column by column First row contains labels First row is a label row Only used for Separate labels by lines Height of the first line Height of the first line in of the other lines First column contains labels First column is a label column Only used for Separate labels by lines Width of the first column Width of the first column in of the other columns Page 119 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Menu Commands z Tree 3 5 Treatment Menu Reference Manual Separate labels by lines If the first row is a label row a dividing line is drawn between the first and the second row The same procedure applies for the first column Separate rows by lines Lines are drawn between the rows Separate columns by lines Lines are drawn between the columns Button position Buttons can be placed into corners or centered at a margin Button arrangement
74. The name is used for file names and for the session name in the output It is enforced that the name contains current date and time sessionprefix prefix Change the session name 11 3 Command line options for z Leaf server adr adr contains the IP address of the experimenter PC name name name is the name the client has in the clients table nameisipaddress The IP address is the name the client has in the clients table size widthxheight Size of the client s window In this way you can test on a large screen how the layout will look on a small screen For example the VGA format is 640x480 There may be no spaces around the x position xpos ypos Position of the client s window with respect to the top left corner There may be no spaces around the comma fontsize size Sets the font size fontface face Sets the font face buttonfontface face Sets the font face for buttons logtime Stores time at which input is made or the screen is updated It uses the time on z Leaf This time is therefore not influenced by network delays On the other hand this time is not synchronized across different subjects logtimelocal The timing information is stored on a local directory on the z Leaf computer xlsdir dir Location where the time file is stored locally on the z Leaf computer xlsdirsrv dir Location where the time file is copied when the experiment is finished It prevents network traffic during the experimen
75. The values of string variable have to be surrounded by quotes Condition Condition whether the tables are loaded The condition is evaluated in the globals table Append Filename Name of a file that contains tables The records of these tables are appended to the existing records of these tables An error message appears on z Tree if the file cannot be found or opened Replace Filename Name of a file that contains tables The records of these tables replace the existing records of these tables Thus the tables in the file replace the current tables This is potentially dangerous if the data has not been stored An error message appears on z Tree if the file cannot be found or opened Example of an input file tablenamel gt tlvarl gt tlstringvar2 gt tlvar3 tablenamel gt 1 gt textu 3 tablenamel gt 4 gt Waele gt 6 tablenamel gt 7 gt Witenes 9 tablename2 gt t2varl gt t2var2 tablenanc2 12 tablename2 gt 13 gt 14 tablename2 gt 15 gt 16 8 3 5 New Table Dumper A table dumper stores tables in the format as explained above in the Table Loader Section Condition Condition whether the tables are stored The condition is evaluated in the globals table Output Filename Name of the file in which the files are stored An error message appears on z Tree if the file cannot be found or opened Page 113 University of Zurich Department of Economics Thurgau Institute of Economics a
76. The waiting screen is shown when subjects wait for the next stage 7 5 What can be contained in stage tree elements In the following we list for all stage tree elements what kind of other elements they can contain We use the notationa lt b cif the element a contains the element b followed by c A star after an element means zero or one or more instances of this kind of element The first line therefore signifies that the stage tree contains one background followed by some stages zero or more The notation a b c means that the term a is one of b or c Page 105 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 The Stage Tree Elements What can be contained in stage tree elements SlLagetrec background stage activescreen waitingscreen box standardbox headerbox helpbox containerbox gridbox calculatorbuttonbox historybox contractcreationbox GoOnisaaicilensielo ox contractgridbox background stage table program activescreen waitingscreen program activescreen waitingscreen box box standardbox headerbox helpbox containerbox gridbox calculatorbuttonbox historybox contractcreationbox contractlistbox contractgridbox messagebox mult imediabox slideshowbox chatbox plotbox item button box item button item tem button H tem button js tem button Ee
77. This means that the last subject s will not see the waitingscreen but instead immediately enter the next stage A period ends when all subjects are in the waiting state of the last stage If it was not the last period the next period starts After the last period the last waitingscreen remains on the subject screen and the subjects state changes to Ready meaning that a new treatment can now be started The Background element in the stage tree contains the information that is not specific to a particular stage In the background dialog you set for instance the number of periods and the number of subjects Then the Background contains the list of tables that are used in the treatment After the tables the Background may contain programs They are executed at the beginning of each period The elements that are contained in the Active screen of the Background are inserted into the active screen of each stage see also Section Section 3 4 Screen layout on layout For instance you can display a header that shows the current period and the remaining time in every stage By inserting it in the Active screen of the Background it is not necessary to include this header in every stage The elements that are contained in the Waitingscreen of the Background are inserted into the waitingscreen of each stage Very often the Waitingscreen contains only a message such as Please wait until the experiment continues In this case this message can b
78. University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Introduction z Tree 3 5 A guided tour of a public goods experiment Tutorial Table subjects Owner Variable if tt Condition Cancel Program j Figure 2 4 Programs are entered in the program dialog Now we add stages to the treatment Stages are steps in a treatment They correspond to the essential screens which are presented to the subjects In the public goods experiment there are two essential screen On the first screen the subjects enter how much they contribute and on the second screen they get to know the other subjects decisions and their income in this period To add the first stage we select the stage tree element Background and choose Treatment gt New Stage A dialog opens In this dialog we can choose some options In our treatment we do not have to change the default options We do only change the name of the stage into Contribution Entry and click the OK button We observe that this stage as any stage contains two elements see Figure 2 5 A stage with the active screen and the waiting screen as shown in the stage tree The Active screen and the Waiting screen The active screen represents the essential screen On this screen a subject gets information and enters the decisions The waiting screen is shown when the subject has concluded the stage It is sho
79. Untitled Treatment 1 2 Figure 3 9 Parameter table dialog The subjects are named S 1 etc and the periods are numbered Trial periods are preceded by the term Trial In the cells of this table programs can be entered These programs are executed for the corres ponding periods and subjects For instance the program in the cell S 2 is executed for subject 2 in every period This means that this program is executed in every period for the second row in the subjects table In this cell we define the role parameters The program contained in cell F is also executed for subject 2 However it is only executed in period 1 the first paid period In this cell we define the specific parameters The program in the cell label with 1 first column is executed in the globals table In it we define parameters that are the same for all subjects but differ from period to period In this cell we define the period parameters The programs in the parameter table can be viewed and changed with the command Treatment gt Info or by double clicking the field in question Whole cells can be copied either with Copy Paste or by se lecting them and then dragging them over from one field to another In the cells of the specific parameters there is a small number in the upper left corner This is the group number This number can be modified in the dialog of the cell or by applying the matching procedures in
80. Windows shortcut dialog There must be a space before and after name and there may be no space after the slash Yourleafname can be any name It must be different for the different shortcuts You can then start the z Leaves by double clicking on the shortcuts You can switch between different programs with the Alt Tab key combination Shortcut to zLeaf exe Properties a 2 x General Shortcut g Shortcut to zLeaf exe Target type Application Target location ztree Target C ztree zLeaf exe name first IV Run in separate memory space J Run as different user Start in Etre Shortcut key Nons Run Normalwindow S Comment Po Eind Target Change Icon cma e Figure 2 10 Windows shortcut dialog You can also start several z Leaves with a batch file Open a text editor and write the text start zleaf exe name first start zleaf exe name second Save this file with a name ending with bat or cmd e g call the file start2leaves bat Put this file into the directory of zleaf exe and run the batch file by double clicking This second method is partic ularly useful if you have to start many z Leaves at once No matter whether you start z Leaf on the computer where z Tree runs or whether you start it on an other computer in the lab you can check how many z Leaves are actually connected with the z Tree you are currently running You do the following In z Tree you ch
81. a set If this box is checked in the previous stage too then the stage before also belongs to this set and so forth Now only one subject per group may be in any stage of such a set Leave Stage after timeout If no input The stage is terminated after timeout if no input is expected Yes The stage is terminated after timeout even if input is expected No The stage is not terminated after timeout Page 111 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Menu Commands z Tree 3 5 Treatment Menu Reference Manual Timeout The number of seconds after which the timeout occurs This expression is calculated in the globals table In the stage tree the stage options are displayed after the name The following notation is used Option Notation Wait for all Start if possible Start if condition Not at most one per group in stage At most one per group in stage A and in previous stage s z If no input leave stage after timeout timeout Do leave stage after timeout timeout A Don t leave stage after timeout timeout N Table 8 1 Stage options notation in stage tree view 8 3 3 New Table A table stores input and calculations Tables are accessed with their names Table Eg Nave foe m Lifetime Cancel C Period C Treatment ei m Program execution When first subject enters stage Alwa
82. ach unit of the good has a value for the subjects and that value differs between the subjects The data is stored in the subjects table in the variables Endowment and ValuePerUnit The following program is supposed to calculate the total value of the good WARNING flawed program Value Endowment ValuePerUnit TotalValue sum Value Consider the following table Endowment and ValuePerUnit are set Value and TotalValue are not yet defined but when accessed the cells already contain data What the values return is undefined but often they contain zero Endowment ValuePerUnit Value TotalValue 2 3 4 5 First Value is calculated for the first record for a value of 6 Then TotalValue is calculated for the first record It returns the sum of 6 and an undefined value probably 0 Endowment ValuePerUnit Value TotalValue 2 3 6 6 4 5 Then Value is calculated for the second record for a value of 20 Finally TotalValue is calculated for the second record It returns the correct sum of 26 Endowment ValuePerUnit Value TotalValue 2 3 6 6 4 5 20 26 This example shows that z Tree processes the program row by row and not column by column However to get a correct value for TotalValue we need to do the calculation column by column We Page 24 University of Zurich Department of Economics Thurgau Institute of Economics a
83. after OK r Leave Stage C Yes C No Normal ie stage is not left after click if stage is left after timeout and button is contained in contract creation or selection box Color Automatic C Gray C Red Event time Figure 8 22 Button dialog Name Label of the button If this consists only of an underscore _ no button appears However the space for the button is kept free No record created or selected If this option is checked for a button in a contract creation box then pressing the button will not create a new record If a button in a contract list box has this option checked then pressing the button will not select a record i e this button can be pressed even if no record is selected Clear entry after OK After the button has been pressed the fields belonging to this button are cleared This option is useful to prevent subjects from making the same entry repeatedly Leave Stage Per default stages are left if the button is in a normal box or if the stage is not an auction i e it waits for input to conclude The options here allow overriding this behavior Color Buttons which are related to input appear in red other buttons in gray This option allows more flexible use of the color Event time If this item is not empty then the corresponding variable is created in the scope of the item in which the button lies This variable is filled with the time of when the event on the client occured in seconds after th
84. als table Furthermore it sets the variable Last Sub ject Done in the globals table to the value of the Subject variable in the subjects table The program runs through the whole subjects table so finally Last Sub jectDone will contain the value of the Subject variable of the last subject 3 2 6 Application Restricting a table function to the members of one s own group An important use of the scope operator consists of calculating a table function restricted to the members of the subject s own group The variable Group contains an ID for the group i e it is 1 for the first group 2 for the second etc In general we want to restrict interaction to groups i e we want to restrict a table function to the members of the own group Suppose that we want to calculate the sum of the variables g in the own group If we know that at most groups 1 2 3 and 4 exist we can calculate s without the scope operator s if Group 1 sum Group 1 g if Group 2 sum Group 2 g if Group 3 sum Group 3 g sum Group 4 g This expression is complex susceptible to error and not general In particular if the number of groups is higher than 4 this expression is wrong Page 28 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Definition of Treatments z Tree 3 5 Interactive experiments Symmetric games Tutorial With the scope operator this
85. ameter table Instead you can set up a tab separated table with the variable values in an editor and import it with the command Treatment Import Variable Table This command is available if the parameter table is the active window If you choose this command you first have to enter the name of the variable you want to import Assume you name it MyVar Then you choose the file where you have entered the values Then the file is processed Wherever there is a nonempty entry in the table then the following line is added to the program of the corresponding specific parameter If the value in the table equals 45 for instance the line added will be MyVar 45 The import just wraps the text in the table with variable and a semicolon Knowing this it is possible to import any program into the parameter table The program only has to start with an assignment However adding a dummy statement at the beginning can easily do this When you have imported variables and program it is useful if they are visible in the representation of the table You can achieve this with the menu commands Treatment Show Variable Treatment gt Append Variable and Treatment Append Text The commands are explained in the reference manual 3 3 6 Importing parameters into a program If you want to import many different values then is also possible to generate a z Tree program in a spreadsheet program Imagine you created the following table
86. ameters specific to the treatment as the endowment 20 and the efficiency factor 1 6 are defined in a program To insert a program select the stage tree element just above the Active screen in the stage tree element Background Initially it is the element called session Then choose Treatment New Program In Figure 2 4 Programs are entered in the program dialog you find the dialog that appears The actual program is entered into the field Program Enter the following code into this field EfficiencyFactor 1 6 return from the PG per invested point Endowment 20 This program defines two variables When the program is executed the variable Ef ficiencyFactor is filled with the value 1 6 and the variable Endowment is filled with the value 20 It is a good practice to define all parameters at the beginning of the treatment i e in the Background This makes the treatment easier to understand and it allows making changes in the parameters at one single place The text after the two slashes contains a comment Comments are not interpreted i e a comment does not change a program s consequences The comment is addressed to the programmer It should make the program more comprehensible for the programmer who looks at the program at a later time Comments are very valuable It is a good practice to put a comment into the first program of a treatment which explains the purpose of the treatment Page 6
87. are responsible for avoiding this You can choose a sufficiently wide first value or place the item into a box with other items that are wider You could use an invisible variable that contains a lot of spaces Note further that labels are evaluated only once at the beginning of the stage Variables in labels are not updated 10 2 Formatting with RTF commands known to be processed In some places texts can be formatted with RTF Labels can be formatted in standard boxes grid boxes contract creation boxes and contract grid boxes The options in the text layout can be formatted in standard boxes grid boxes contract creation boxes and contract grid boxes Finally texts in help boxes and message boxes can be formatted The RTF format begins with rtf with a blank space at the end and ends with In between is the text to which formatting instructions can be added In options of text layouts the rtf has to appear in every option leeres ISU Nees Wo onah Se 2S ieese Wo icwiols Page 168 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Text Formatting z Tree 3 5 Formatting with RTF commands known to be Reference Manual processed Formatting instructions begin with and end with a blank space If a formatting option is supposed to apply only to a certain range you can place this range in curly brackets Not the whole RTF is supported The most important
88. ariable If it is an input variable this is the name of the question as it should appear in the data file If input is not set it has to be a variable of the session table Type Layout of the question Text Number A text field appears into which input is entered In the case of the number option there is a check to see if it is really a number that has been entered Furthermore the check determines whether the number is in the valid range If the option Wide is selected for a text field the entry field may consist of several lines The number of lines can be selected Buttons A button is created for every line in the field Options Of course only one question with this option is permitted per question form Radiobuttons A radio button is created for every line in the field options These buttons are arranged vertically one on top of the other Slider Scrollbar The slider and scrollbar make a quasicontinuous entry possible Minimum maximum and resolution need to be entered In the wide layout a label can be placed at the margins These labels are entered in the field options The maximum is always the value at the right border the minimum is the value at the left border Maximum may therefore be smaller than minimum Radioline A radio button appears for all possible answers determined by minimum maximum and resol ution In the wide layout a label can be placed at the margins These labels are entered in the Page 90 University of Zurich D
89. atching The first players constitute group 1 the next players group 2 and so on The stranger matching is a random matching i e in every period the group is determined by the computer s random generator The commands in this menu set the Group variable in the specified way So if you change the number of subjects or the number of groups you have to reapply the command More flexible matchings can be entered in the parameter table that will be explained in Section 3 3 3 The parameter table In addition you can specify the matching in a program which is explained in Section 3 3 10 Programming group matching 3 2 8 Summary statistics The tables mentioned so far are reinitialized after each period of course after being stored to the disk So for the experimenter in the lab they disappear from the screen To keep an overview of the course of the experiment you can use the summary table The summary table contains one record per period but the table is not reinitialized at the end of a period It is not initialized until the treatment ends If you run a program for the summary table the program is only executed for the record of the current period Look at this example AvProfit subjects average Profit However if you apply a table function the program runs through all records If you want to restrict the program to the current period you have to add the condition same Period Page 29 University of Zurich
90. ate system and makes it possible to display plot items Plot items are drawn sequentially meaning that items lower down in the list of items can cover items higher up in the list The Plot box is opaque and covers all boxes below it Horizontal margin Vertical margin Fill color ee 5 _Filcole 7 Maintain aspect ratio x axis y axis C categorical linear C logarithmic C categorical linear C logarithmic left 100 top 100 right 100 bottom 100 Move pointer to Figure 8 19 Plot box dialog Horizontal margin Distance from the frame of the plot box to the beginning of the plot area Measured in pixels Vertical margin Analogous Fill color Color of the plot area Maintain aspect ratio When checked ensures that units horizontal and vertical are the same actual size in case the z Leaf screen is not square categorical The extent of the range is increased by 0 5 in both directions So categories 1 to 7 range from 0 5 to 7 5 which is a distance of 7 linear Linear units define the coordinate system logarithmic Logarithmic units define the coordinate system left right top bottom Determines the boundaries of the coordinate plane the plot box creates Move pointer to Whenever this box is displayed e g when it is shown for the first time and when it is redisplayed after it has been hidden by setting the display condition to FALSE the mouse pointer is moved to the corresponding x and y position If both fields are empty
91. ation with a file server The easiest way to install z Tree is to put z Tree and z Leaf in a common directory on a file server The server must have both read and write access to the directory while the client should only have read access When z Tree starts it writes the IP address of the server PC into the file server eec in this directory The z Leaves read the address of the server in this file and connect with z Tree on this machine 6 2 Installation without a file server z Tree and z Leaf can run on different computers that do not have access to a common file server This option is needed if you want to run experiments over the Internet As opposed to an installation with a file server there is no easy method for z Leaf to know where z Tree is running Therefore z Leaf must have the file server eec the file contains the IP address of the server in its directory or in the directory c expecon conf z Tree s IP address can also be set with the command line option server ip address when the client starts up If z Tree and z Leaf do not run from a common directory the function Run gt Restart All Clients does not work If there is a problem the clients have to be started up manually 6 3 Setting up a test environment You do not need several computers to test programs You can start z Tree and more than one z Leaf on one computer However you have to give the z Leaves different names For this you use the command line option
92. ator creates a new small table that contains one variable When a table function or a do statement is applied to such an iterator it corresponds to a loop over the values contained in the table An iterator has the syntax iterator varname runs from 1 to number of subjects iterator varname n Y R SOT IRGO iterator varname x y Yi UNS aeRO A CO Y iterator vanamen xX y da runs from x Co y wich Steps of di This syntax defines a table This table has a variable varname and records for which the variable varname is filled with in the last case for instance the values x x d y Example two ways of calculating squareSum 1 4 9 16 25 55 souare coumi aiieicaicos 2 1 S Sum a a s Vane squareSum 0 earar oa al 3 oClo squareSum squareSum i i iterator has its own scope 3 9 3 Example Cost function using arrays How can different marginal costs and redemption values be assigned to different subjects in an auction Either you use an array i e an indexed variable or you use a separate costs and a separate redemption value table as explained in Section 3 6 12 Examples of double auctions To do it using arrays define the arrays for the marginal costs and the redemption values in the subjects table in the Background To do so you first write the array Page 69 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2
93. be undertaken in descending order the expression is preceded by a minus sign Line color Used to connect points in the plot graph Line width Used to connect points in the plot graph Fill color Used to fill the polygons that are defined by points that are contained in the plot graph Fill to x axis Instead of filling polygons it creates an area plot i e it fills the area between the points that are contained in the plot graph and the x axis Connect to previous point Whether the different records in the given table should be connected by a line as they are represented on the screen 8 3 31 New Plot Text Plot Text Name ooo horizontal alignment vertical alignment G left C top first line C center bottom center right Orientation 90 90 text color rgb 0 0 0 Font bold italic underline Display condition Figure 8 29 Plot text dialog X y Where the text is to be located Page 136 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Menu Commands Treatment Menu Width Width of the box containing the box horizontal alignment vertical alignment How the text is aligned in relation to x y Orientation 90 90 Rotates text text color In rgb Font In pixels 8 3 32 New Line Plot Line Name oo Point 1 arrow size arrow width F Arow is closed line color line width Display co
94. before the chat text For example with what is written in the output text space on the left the subjects will see what is written in the right hand area when a subject types Hello world into the chat entry area Participant says Hello world lt gt Participant says lt 1 gt Wrap text Self explanatory If this is not selected if there is text that extends beyond the screen width a scrollbar will appear Output text centered Output text is centered rather than the default left aligned Page 126 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Menu Commands z Tree 3 5 Treatment Menu Reference Manual 8 3 23 New Slide Show A slide show is a timed display of plot boxes It has to contain slides or slide sequences The plot boxes have to be contained in slides Skip delayed slides Checked if checked slides have to be omitted if it took too much time to process the previous slide s 8 3 24 New On Off Trigger The on off trigger item can be placed into any box before other elements e g items or buttons As buttons and plot input items it can contain checkers and programs The starting scope of programs is the subject s record in the subjects table Name mR Condition mance What on show ON onhide OFF Event time Figure 8 21 On Off Trigger dialog Condition The condition is evaluated on the client It allows activatin
95. bjects in the group Of course in this treatment we could also write N 4 However the formula above allows us to run this treatment with different group sizes without changing any line of program In the last line we calculate the payoff for the subject The predefined variable Profit is used for this This variable is special because at the end of each period this variable is summed up At the end of the session you can easily generate a file the so called payment file that contains for each subject the sum of the profits made during the whole session Now we define the profit display screen First we insert a standard box into the Active screen of the Profit Display stage Then we insert three items into this box We show the own contribution Page 9 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Introduction z Tree 3 5 First test of a treatment Tutorial the sum of all contributions and the subject s income for the period We insert the items that show the subject s own contribution and the sum of all contributions as explained above In the item that displays the subject s income we enter 1 into the field Layout because we want to show the variable Profit with one digit precision The profit display screen also has a button We name this button cont inue because the subjects do not have to confirm anything The button just allows the sub
96. bles In this chapter an overview of more sophisticated layouts is given In the real battle of the sexes game for instance the players can choose between boxing and opera In the implement ation above the subjects had to enter a number for their choice In this section we will present how input can be made with different forms of user interface elements such as text input radio buttons check boxes and sliders Furthermore we show how information can be displayed and arranged on the screen Page 41 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Definition of Treatments z Tree 3 5 Screen layout Tutorial 3 4 1 Layout in the small the item Items are used for displaying and reading in variables An item contains the name of the variable and information on how to display it We call an item an input item if the checkbox Input is checked In this case subjects must make an entry We call an item an output item if the checkbox Input is not checked In this case a variable will be displayed Variables contain numbers or strings Numbers can be displayed in different forms These forms are defined in the Layout field of the item dialog If a number a variable or an expression is entered here then the value of that field determines how the variable is rounded when it is displayed If for instance 0 2 is entered in Layout and the variable contains the va
97. buttons This happens by putting a program within the button as shown in the figure as well Page 85 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Definition of Treatments z Tree 3 5 Complex move structures Tutorial amp Background globals Name with Frame amp subjects Pie Distance to the margin p Adjustment to the remaining box amp summary Width p 50 Cancel amp contracts Height p 507 I top 2 session I left a J right logfile bottom 6 Active screen E l E Header iti Displa aa 6 Waitingscreen Pt aie Showlnfo 1 dE Text 2 Please wait until the experiment continues Stage 30 Buttons Position Arrangement X amp subjects do ShowInfo 0 e e C Intows o Active screen 2 o 9 Cincom S E input box CC e 2 Please make your input here IN x 3 Show Instructions S subjects do Showlnfo 1 om 2D You can transfer or not If you do not transfer you and the other pli Return to decision A subjects do Showlnfo 0 E Waitingscreen Figure 3 49 Display condition example 3 13 3 Moving back Stages are always processed sequentially It is not possible to return to previous stages If you want to let subjects move back and forth you can simulate stages using boxes A good example are instructions organized in pages You will want to allow subj
98. buyers offers and the box of the buyers offers are positioned next to each other side by side Page 56 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Definition of Treatments z Tree 3 5 Continuous Auction Markets Tutorial 3 6 4 Making an offer In this section we describe how to design a box for making an offer Offers are made in a contract creation box You insert a new contract creation box as you do any other box from the menu The dialog of the contract creation box contains some fields that are specific to this type of box These options are explained in detail in the reference manual For this example the options are set properly by default The only thing that you have to change is the positioning Similar to the standard box contract creation boxes can be filled with input items and buttons In our contract creation box the offer must be entered i e we place an input item for the variable Price into the box To confirm the offer the subjects have to press a button This button is also placed into the contract creation box When a subject presses this button a new record in the contracts table is created The data in the input items i e the data in the variable Price is stored in this record How do we fill the other information into the record We do not want the subject to have to make an entry for all the information in this new record This se
99. can be entered Options The labels of buttons radio buttons and in the wide layout of sliders scrollbars and radio lines Text or number Text or number radiobuttons eee our radiolinelabel left right POE A radioline see amp amp Cp checkboxes TM we TN left right Lo re a E E O E E n j E slider En n checkboxes TM scrollbar gt rN buttons ro a slider scrollbar Maim oR buttons a hn a Figure 4 1 Layout of questions normal layout left and wide layout right Page 91 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Questionnaires z Tree 3 5 Running a questionnaire Tutorial 4 2 4 Profit display If you wish to display the earnings made in the session to the subject you use a question form where you can also show variables from the session table These include FinalProfit Sum of all earnings from the treatments MoneyAdded Money injected by the subject see bankruptcy procedure ShowUpFee Amount of show up fee MoneyToPay Showupfee FinalProfit MoneyAdded MoneyEFarned Showupfee FinalProfit This is the value used in the payment file 4 2 5 Rulers Rulers are used to set the regions where labels and questions are positioned Distance to left margin The position can be given in points or in percentage of the screen width Distance to right margin The position can be given in points or in percentag
100. ce CEY t PSU UW suoteeceue WY Page 159 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Programming Environment z Tree 3 5 Programming language Reference Manual Terminal elements NAME letter letter digit NUMBER real BOOPVAT UCT ENEAS Warieigna ts FUNCT IONNAMEO gettime pi random randomgauss FUNCT IONNAME 1 Walos wacan Seher e ce eos Yezo vlen ila Whee iesincloimnonresom Valm Wis aitewy Erim upper lower FUNCT IONNAME 2 Weommec mess mim moct Mpower Y souncl Vioumelslorin reece Sieresimcie muimlesie s FUNCT IONNAME3 umide tpost BOOLFUNCTIONNAME1 not BOOLFUNCTIONNAME2 and or BOOLFUNCTIONNAME1R same TABLEFUNCTIONO count TABLEFUNCTION1 average find maximum median Vinalinsienmn Vorocmer Ysieckliew Weis TABLEFUNCTION2 pearsoncorr regressionslope spearmancorr BOOLOPERATOR2 amp COMPOPERA OR Well We w gt Ww wu SCOPMOMMVATOR g ew Wile Page 160 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Programming Environment z Tree 3 5 Programming
101. cond price auctions The experiment The participants bid for a good which has a private value to them If they get the good their income will be their private value minus the price they pay To get the good they simultaneously submit an offer The person with the highest bid is the winner and gets the good The winner has to pay the second highest bid If the two highest bids are equal he has to pay this highest bid In this example all members of a session will be in one group though naturally the program can be modified to have multiple groups The solution B Bid 30 4 subjects do privateValue roundup random 10 01 Active screen EA Standard E0 Your private value OUT privateValue E0 Enter your bid IN Bid OK GB waitingscreen B Profits 30 subjects do potentialwin if id maxirnum id 1 0 winID if potentialwin 1 Subject count Subject lt Subject amp potentialwin 0 0 globals do winlDwinner roundup subjects maximum winID randomd 1 to randomly select a winner in case of multiple highest bids subjects do win if winID winlDwinner 1 0 5 Q subjects do TE price maximum win 0 Bid subjects do Profit if win 1 privateValue price 0 I Active screen EX Standard ED lt gt lt if win 1 1 0 text 1 You were the highest bidder You will pay the following price lt price 01 gt O Someone
102. culation of Diff we would not calculate Best Diff correctly because we do not know the value of Di ff for the records later in the table In the current implementation an empty value is set to zero So for all subjects except the last one Best Diff would be calculated as zero If we put the calculation of Best Diff into a new program everything is done correctly First the first program is calculated for all records i e for all subjects Then the second program is calculated for all records At this moment Diff is calculated for all records and we can apply the table function minimum In the next statement we determine the winner s We put 1 into the variable IsWinner if a subject was Closest and 0 otherwise IsWinner if Diff BestDiff 1 0O The if function takes three arguments The first argument is a condition Diff BestDiff If this condition is satisfied the second argument is the result of the if function i e 1 If the condition is not satisfied then the third argument of the if function is the result of the if function i e 0 Next we calculate the number of winners to deal with the ties We have to place this statement into a new program again because in the table function sum we use a value that is calculated in the program above NumWinners sum same Group IsWinner Finally we calculate the profit It is zero for those subjects who did not win IsWinner is zero and it is Prize 1 NumWinners
103. current record With the scope operator we may go back to the variables of the old current record the record that lies outside the table function In this respect the scope oper ator gives us access to a wider scope of cells When a table function is carried out within another table function this results in an expression of this table function with three records that are accessible Let us consider the following expression where all three tables ta tb and tc contain a variable v In the expression of the product V is the variable in the current record of table tc the scoped variable V is the variable in table tb and only by doubling the scope operator V do we reach the cell in the current record of table ta The line underneath the ex pression specifies which V is being used at a particular place x Wa ido sim WY sW teeypkocum e W Y ssy J I Lh ea aes isiel ea ta In this example the variable V occurs in all tables However it may happen that a variable only occurs in one table In this case you may omit the scope operator Let us suppose that the variable A occurs only in the table ta B only in the table tb and C only in tc Then the following expressions are equivalent IX ap Scio Sim W a e ga eezipiocion gi ge x SIN a ico sim B A ce procer B A Page 26 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015
104. cution 33 3 3 2 Calculating different values for different subjects 34 3 3 3 The parameter table 35 3 3 4 Group matching 36 3 3 5 Importing parameters 37 Page ii University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Table of Contents z Tree 3 5 3 3 6 Importing parameters into a program 37 3 3 7 Exercise General 2x2 game 37 3 3 8 Example First price sealed bid auction 39 3 3 9 Example Private value second price auctions 40 3 3 10 Programming group matching 41 3 4 Screen layout 41 3 4 1 Layout in the small the item 42 3 4 2 Layout in the large Screen design and boxes 42 3 4 3 Placing boxes 43 3 4 4 Basic box types 44 3 4 5 Button placement 47 3 4 6 Background layout 48 3 4 7 Insertion of variables into the text 48 3 4 8 Text formatting with RTF 49 3 5 Sequential games 50 3 5 1 Sequential moves 50 3 5 2 Simultaneously in different stages 51 3 5 3 Ending a stage 52 3 5 4 Example Ultimatum Game 52 3 6 Continuous Auction Markets 54 3 6 1 Concepts 54 3 6 2 A double auction in the contracts table 55 3 6 3 Preparing the layout for the auction 56 3 6 4 Making an offer 57 3 6 5 Viewing offers 57 3 6 6 Do statement 58 3 6 7 Accepting an offer 58 3 6 8 Checking subjects entries 59 3 6 9 Auction stages in detail 60 3 6 10 Creation of new records in the program 6
105. d Run Shuffle Clients respectively The clients table has five columns Client Name of the client In general this is the name of the subject PC If a client is no longer connected its name appears in brackets If a client with the same name should reconnect it can continue at the same place where the previous subject left off The caption to the clients table gives the number of clients currently connected State The state in which the subject is at a given point Example Ready when the subject is waiting for the next treatment or for the next questionnaire The state is abc if the subject is in the active screen of stage abc and abc if the subject is in the waiting screen of stage abc Profit Accumulated income made in the previous treatments The profit made in the current treatment is not included This profit is indicated in monetary units Fr as various treatments may have different exchange rates Show up fee invested TRUE if the subject has suffered losses and has declared himself ready to account for these with his her show up fee Money added Extra money that the subject has injected into the game after losses in order to be able to continue This sum is of importance for the calculation of losses The profit in the payment file is always the net income the subject has gained from the experiment At the hour of payment injected money must therefore be added to the amount indicated in the
106. d Words The text Player is included before each chat message but is not a variable so does not have to appear within the lt gt The variable ID is a numerical variable and we want it to be represented Page 80 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Definition of Treatments z Tree 3 5 Free form communication Strings and other Tutorial data types as such so after the we use the number 1 to indicate that the layout is numeric in whole numbers Since Words is a text variable the layout code is 1 With this our chat environment is now finished 3 11 2 String operators and functions In z Tree version 3 4 strings have been implemented as variables meaning it is possible to modify or analyze text such as the chat messages we have just discussed As an example we will make a program that counts the number of characters it takes until a smiley emoticon first occurs in a written text In addition to the chat box text can be written in a standard box Here however the return key does not function to send a chat message In the first stage insert an input item into the standard box Write to your partner here up to 100 characters Cancel Variable fchat Layout Istring IV Input Minimum 0 Maximum 799 Show value value of variable or default Empty allowed Default Figure 3 43 Input item f
107. d for this record Programs in other tables X and programs in the target table with a condition are executed for all the record in X as well as the selected records in the target table The fol lowing rules apply The programs are run one after the other for all necessary record combinations Within a program the program runs through the records of X for the first relevant record in the target table then through the records of X for the second relevant record in the target table and so on 9 2 5 Summary In a nutshell programs executed at the beginning of the period are executed in the corresponding table with access to the globals table and other tables in the scope environment Programs in buttons and plot input items are executed in a scope environment that allows to access the record of the subject who pressed the button and the structure selected 9 3 Program execution Programs at the beginning of a stage are executed one after the other If the Start option in the stage is set to Wait for all the procedure is as follows First the first program is executed for all subjects Then the next program is executed for all subjects and so forth Note that setting the value of Participate to zero does not stop program execution Participate does not take effect until all programs have been executed Page 164 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Programming Enviro
108. d the clients need to be in the state Ready 8 5 7 tablename Table Opens the window showing the table or brings it into the foreground 8 5 8 Stop Clock Stops the clock However subjects can still make entries If for instance all subjects click continue the session continues regardless of the stopped clock 8 5 9 Restart Clock The clock is restarted 8 5 10 Discard a client The client selected is discarded It can be replaced by a new client In case of a defect in a subject PC the following needs to be done The client in question is clicked in the clients window Then the menu Discard a client is chosen With this the client is discarded The new PC is started The client then appears in the lowermost row of the clients window It first has to be selected and then moved over the old client Doing this the mouse has to be released for an instant If the mouse is not released this procedure only selects the space between the new and the old client 8 5 11 Leave Stage The subject whose state is selected leaves the stage If a client is in an active screen it can be moved on to the waiting screen of the stage This option is useful when testing program In an ordinary session it should not be necessary to use this command Note that you have to select the subject s state in the clients table There is the variable LeaveStage which does the same from within a program When this variable is set to 1 the client goes to t
109. d to period In z Tree the subjects table is set up freshly in every period so the information about earlier periods is not available directly However the tables of the previous period can be accessed with the prefix OLD So if you want to copy a variable Stock from the previous period you write ie Pexiloc gt 1 4 Stock OLDsubjects find same Subject Stock Page 83 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Definition of Treatments z Tree 3 5 Complex move structures Tutorial There is no way of accessing data from even earlier periods If you need to access more information you can use table with lifetime treatment or even session 3 12 3 Copying data from treatment to treatment with the session table Consider the following experiment First you run a public goods treatment The income earned in this public goods treatment can then be used in a second treatment in a market game Because the session table survives the end of a treatment you can solve the above problem elegantly In the first treatment you store the total profit in the variable Income in the session table and in the second treatment you can access this variable again How you can store data in the session table In programs in the session table the corresponding record of the subjects table can be accessed with the scope operator Therefore in your first treatment you can
110. dify this value in the dialog or with the menus in the Treatment Matching menu So you can for instance define fixed partner or random stranger matchings Whenever you apply a matching command this command is applied to the selected area in the parameter table or if there is nothing selected to the whole parameter table The matching com mands directly modify the number in the upper left corner in the cell of the parameter table They do not define a logical matching structure So if you change the number of subjects or periods in a treatment you have to reapply the matching command You can also change the Group variable in programs This allows endogenous matching or the definition of matchings that are independent of the number of subjects see Section 3 3 10 Programming group matching Page 36 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Definition of Treatments z Tree 3 5 Symmetric simultaneous games Tutorial 3 3 5 Importing parameters Entering the values into the parameter table by hand is only reasonable if there are not too many variants It is for instance useful if there are a couple of parameter combinations which differ from period to period in an unsystematic way If a parameter is different for all periods and subjects it becomes imprac tical to double click the field in question and to adapt the program for every cell of the par
111. dir temp Shortcut ztree test is used for testing and starts z Tree with witee Exe che testtrash learchir yalleeut Experimenters have read and write permission in all directories Subjects have read permission in the zleaf directory We have placed z Leaf in a different directory from the directory where z Tree is located The subjects only have access to this directory and they have only read access to it This prevents subjects from getting access to your experimental data To be able to automatically start the z Leaves wherever z Tree is started we set the leaf directory in the options of z Tree Page 100 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Reference Manual 7 The Stage Tree Elements 8 Menu Commands 9 Programming Environment 10 Text Formatting 11 Command Line Options 12 The Import Format 102 108 154 168 171 175 The Stage Tree Elements z Tree 3 5 Editing in the stage tree Reference Manual 7 The Stage Tree Elements This chapter explains options of the stage tree elements that cannot be created The stage tree elements that can be created are explained in the respective menu section 7 1 Editing in the stage tree 7 1 1 Viewing Branches of the stage tree can be opened and closed 7 1 2 Adding elements Stage tree elements are added from the menu 7 1 3 Deleting elements Stage tree elements can be deleted
112. distributed number between 0 and 1 pi returns 3 14159 and the round function rounds the resulting number to a precision in this case of 001 This corresponds to a precision of three digits The input variable Y must be between 0 and 1 and we let the subjects enter a precision of at most three digits This information has to be entered in the item dialog of the input item The payoff calculation is straightforward First we calculate the sinus function Because the subjects can only enter a finite precision we round the value to the same precision as that of the subjects entries Then we calculate the absolute difference between the actual value and the guess entered Finally we calculate the profit in this period SIn ound Sa 0O Dulce alos Snos XW Ne prore 100 LOO Durr In the active screen of the profit display stage we show this information to the subjects Page 22 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Definition of Treatments z Tree 3 5 Interactive experiments Symmetric games Tutorial 3 2 Interactive experiments Symmetric games With the knowledge of the previous chapter you should be able to program a treatment for an individual decision making problem In this section we explain how to program interactive experiments The dif ference between an individual decision making problem and games is the fact that in games t
113. dom All but the last form of a questionnaire must have a button 8 4 7 Expand all Shows all elements by expanding any nested elements i e elements contained within other elements 8 4 8 Check Checks the questionnaire 8 4 9 Language Sets the language for elements that are newly created as address forms All texts within these elements can be modified later i e they can also be translated later 8 5 Run Menu 8 5 1 Clients Table Opens the clients table The clients table shows which clients are connected to the server It also contains information about the state of the clients i e which screens are currently being displayed to the clients You may open the clients table with the first command from the Run menu Page 147 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Menu Commands z Tree 3 5 Run Menu Reference Manual Each line corresponds to a subject This subject is seated at a PC on which the client is running column Clients As long as no treatment is started the clients can be moved As soon as you start a treatment the order of the clients is fixed After a treatment has started only those clients that are not taking part in the current session can be moved These clients are listed at the end of the table So long as no treatment has been started the clients can be sorted and shuffled with the commands Run Sort Clients an
114. e optionl valuel option2 value2 subelementl subelement2 The sub elements have the same structure Exporting a treatment or a questionnaire supplies the options Page 175 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Index Index Symbols 154 button 131 checkbox 131 radio 130 radioline 130 radiosequence 130 scrollbar 130 slider 130 Istring 131 Itext 130 amp 155 154 154 154 adr 98 172 gsf 98 172 pay 98 172 sbj 98 172 xls 98 172 173 154 adrdir 172 asksessionname 173 buttonfontface 173 channel 172 checkdiskspace 172 counttriggers 173 datadir 172 fontface 173 fontsize 173 gsfdir 172 keyfromserial 174 language 171 leafdir 172 logtime 173 logtimelocal 173 name 173 nameisipaddress 173 paydir 172 position 173 privdir 172 sbjdir 172 server 173 sessionprefix 173 size 173 z Tree 3 5 tempdir 172 treatment 172 x sdir 172 173 x sdirsrv 173 zttdir 172 155 lt 154 lt 154 154 gt 154 gt 154 db txt 172 lastclt txt 172 prevdb txt 172 155 155 A abs 156 active screen 18 active state 18 addition 154 address form dialog 144 and 156 array 69 array statement 155 assign statement 155 assignment statement 16 atan 156 auction double 55 Dutch 65 sing
115. e all Tables Stop Clock Fi2 Restart Clock Shift F12 Stop after this period Replay Leaf From GameSafe Restart All Clients Restore Client Order Reload database Figure 2 14 How to skip stages for testing purposes If a stage has an input field you will get a warning message as shown in Figure 2 15 The warning message when leaving a stage where subjects should make input This is a safety mechanism for real experiments so that you do not skip stages in which you wish to gather important subject data In general the leave stage option should not be used during a real experiment session but only for program testing purposes Page 13 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Introduction z Tree 3 5 First test of a treatment Tutorial WARNING In this stage the subject has to make input You do not get this input if you leave the stage Cancel not leave OK leave Figure 2 15 The warning message when leaving a stage where subjects should make input Checking a treatment means that you check whether everything is calculated as you intended and that the screens look fine If you find an error you have to correct it or at least try to correct it and test the treatment again How do you correct errors The easiest way to correct a program is to double click the stage tree element of the program Then you can edit i e m
116. e In the standard box we see the items and the button we defined in the stage tree We can now enter a value between 0 and 20 into the field next to the text Your contribution to the project and click the OK button If we enter an illegal value such as 25 7 or 2 2 a message informs us that such an entry cannot be made In z Tree in the Clients Table you can observe the state the subjects are in For each stage there are two states The active state indicated with stars corresponds to the active screen and the wait state in dicated with a dash corresponds to the waiting screen This enables you to check whether there are still subjects who have to make their entries When subjects make entries you can observe their decisions in the so called subjects Table This table can be opened from the Run menu Figure 2 13 Clients table with subjects in different states shows the situation where subject first has made her entry and the subject second has not yet done it Page 12 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Introduction z Tree 3 5 First test of a treatment Tutorial Edien Teha Clients Table E ren ais eo Saori Contribution Entry 17 Figure 2 13 Clients table with subjects in different states After all subjects made their entries their profits are calculated and displayed Because in the profit disp
117. e comfortable way z Tree automatically writes it s IP address into the current directory in the file serv er eec If z Leaf is started from the same directory on the same PC or on another it reads this file If z Leaf does not find this file it looks for it in the directory c expecon conf on its computer If it is unable to find either it can take the IP address of the local machine It can now seek the server at this address If the server is not found here either the person who starts the client is asked if he or she would like to try again Page 95 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Conducting a Session z Tree 3 5 How to fix the name of a client Tutorial 5 5 2 Channel and TCP ports If you want to run more than one z Tree on one computer they must work with different channels i e you set the channel with the command line option channel ch to values greater than zero The channel determines the TCP port used in z Tree to listen for connection attempts from the z Leaves The actual port is 7000 channel defaults to channel 0 port 7000 z Leaf listens on port 7999 or lower for a restart message 5 6 How to fix the name of a client If z Leaf is started up by means of a name on the command line e g zleaf exe name T1 this will be the name of the client e g T1 Otherwise the name will first be sought in the file name eec in the
118. e 27 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Definition of Treatments z Tree 3 5 Interactive experiments Symmetric games Tutorial 1 2 3 9 33 9 6 9 36 45 18 3696 5 3 3 2 3 8 17 2 3 30 2730 4 5 6 9 33 18 12 18 36 45 72 3696 5 12 12 8 12 8 17 32 192 30 2730 3 2 5 The do statement Table functions permit read access in other tables There are situations in which this is not sufficient there are situations in which we want to change a variable in another record or table The most important applications are presented in Section 3 6 Continuous Auction Markets Here we present the logic and give a first application With the do statement calculations can be carried out in all records of a table With do statements the program statements is executed for all records in the current table As in the table function it is possible to precede the do statement with a table name By doing this cal culations are carried out in the table in question As in the table functions you may also use the scope operator here Example Assume the following line is executed in the globals table subjects do Money InitialMoney LastSubjectDone Subject It sets in all records of the subjects table the variable Money to the variable InitialMoney in the glob
119. e Group variable has the same value as ours and the Sub ject variable is different This is expressed in the command OthersChoice find same Group amp not same Subject Choice Finally the profit is calculated with a nested if function Page 38 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Definition of Treatments z Tree 3 5 Symmetric simultaneous games Tutorial Prorit if Choice 1 if OthersChoice Patt Waly Yop 1 iit CeleiesChoneSe 1 PaVil wie je In this payoff function the parameters in the parameter table are used There are many solutions to solve a particular problem Let us also sketch an alternative solution We could define a variable Type for the two types of players Then we define the two payoff matrices in the globals table In the parameter table we only set the Type variable Finally the payoff calculation is a bit more complex because we have to distinguish between the two types 3 3 8 Example First price sealed bid auction Ina sealed bid auction the bidders place secure bids i e bids that cannot be viewed by the other bidders At the close of the sealed bid auction all bids are available for review and the highest bid is evaluated for award In this type of auction the problem is to avoid ties i e the possibility that two or more sealed bids are the same To avoid ties you can add a rando
120. e asked first so that the payment file can be written This is the file that contains a list of the names and earnings in the experiment It is not necessary to include names if you have privacy concerns but an option Next additional question naires are inserted Then a screen that displays the subject s earnings is inserted and finally a good bye screen appears where subjects get instructions where to get their payment A questionnaire consists of a series of question forms One question form displays the individual questions in the same way as the items in the standard box of a treatment However the questions do not appear vertically centered and adjusted to the screen size Therefore question forms may be larger than the screen If this is the case a scrollbar appears The answers in questionnaires are of no consequence which means that they are not entered into a database The answers are only saved as text and cannot be used in programs The question forms are worked through one after the other When all subjects have answered all question forms they are in the state ready and you can start a further treatment or a further questionnaire It is generally impractical to start several questionnaires one after the other because this leads to unnecessary waits It is better to integrate all forms into one questionnaire file The last question form remains on the users screens until you continue i e until you start a new treatment o
121. e box is visible This allows for turning the media file on and off File name Resizing options Video Sound options I Enlage to fit Volume 0 100 T Shrink to fit Start after sec r l Do repeat Allow user control I Rewind Figure 8 18 Multimedia box dialog File name Name and path of the media file Supported file types are jpg gif png bmp wmv mpg avi wav and mp3 The files are played using Microsoft Windows Media Player Enlarge to fit If the image is smaller than the box it is enlarged Shrink to fit If the image is bigger than the box it is scaled down Maintain aspect ratio If the image has to be stretched it is stretched equally horizontally and vertically Volume 0 100 Volume of the sound Default is 0 Start after sec Normally movies and sound start immediately after the box is displayed i e usually at the start of the stage With this option the start of the movie or sound can be delayed Page 124 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Menu Commands z Tree 3 5 Treatment Menu Reference Manual Do repeat The movie or sound is repeated indefinitely Allow user control The user gets a control panel to move the movie or sound back and forth Rewind If the box is turned off hide the movie or sound will play from the beginning when turned on again 8 3 21 New Plot Box The plot box sets up a coordin
122. e defined in the Background and the waitingscreen in each stage can be left empty Figure 3 3 Course of action shows the relationship between the elements in the Background and the elements in the stages in an abstract example with two stages Background programs active screen waiting screen Stage Ww Ww programs active screen waiting screen Stage WwW v programs active screen waiting screen Figure 3 3 Course of action Page 19 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Definition of Treatments z Tree 3 5 Simple experiments without interaction Tutorial Each stage starts with some zero or more programs Then subjects are shown the active screen and the waitingscreen The Background contains the list of tables programs that are executed at the beginning of the period and screen elements that are inserted in every stage 3 1 4 The Stage tree The stages of a treatment are depicted in the shape of a tree diagram called the stage tree Figure 2 9 Stage tree of the public goods experiment above shows the stage tree of a public goods game All elements of the treatment are arranged hierarchically in this figure Stages contain programs and screens screens contain boxes and boxes contain items In order to have an overview you can expand and collapse the lower hierarchy levels as you
123. e number of periods for which we have calculated absolute typed stranger is listed The values for which it is known that it is the highest possible value are given in boldface 1 2 3 4 5 6 7 8 9 10 11 12 subj per type quick calculation available on file Avail on file prov NNWWAAHNMNWAH NW Y os oo p po Figure 8 34 Absolute typed stranger matching Page 143 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 enu Commands z Tree 3 Mi C d Tree 3 5 Questionnaire Menu Reference Manual Transform Allows making transformations on the matching There are three options Add You can add a fixed number to the group ID Multiply You can multiply the group ID with a fixed number Shuffle You can shuffle the group IDs within the period With this command one can for instance easily define matching groups Using matching groups is an important experimental technique because in a stranger matching there is generally only one independent observation per session With matching groups one can define a stranger matching with more than one independent observation For that the subjects are divided into two or more sub populations Subjects are only matched within these sub populations Therefore these sub populations constitute independent observations Example You have 24 subjects with groups of 3 and you want to make two
124. e of the screen width Distance between label and item This is the horizontal distance between the label and the question Half of this distance is also kept to the left and right margins Size of label This is the maximum width of the label When the display is given in a percentage this refers to the width between the left and right margin and not to the width of the whole screen 4 2 6 Buttons Buttons conclude question forms You cannot define more than one button per form However this button can be positioned anywhere on the form The label of a button can be selected by you 4 3 Running a questionnaire At the end of a session the experimenter always starts a questionnaire with the command Run Start Questionnaire which is described below This questionnaire must include an address form a prompt for the subject s address or a virtual step if you do not wish to ask subjects for their address information in order to write the payment file When all subjects have gone through the address form z Tree writes the payment file You may also insert a questionnaire at another point in the session However as questionnaires do not contain information regarding the number of subjects they can be started at the earliest after the first treatment e g the welcome treatment If more than one questionnaire contains an address form the address only needs to be entered in the first questionnaire In subsequent question naires only the
125. e or in the stage tree above It is a good practice to define variables at the beginning of a treatment You can also use comments to explain the purpose of each variable see Section 3 1 2 Comments This makes the program much more easily accessible for other experimenters Examples of assignment statements p 20 Q ql q2 Profit Endowment Contribution EfficiencyFactor Sume Ny Cost exp Effort k We have seen that the globals table contains exactly one record Other tables may contain more records If a program is executed in such a table there is always one record for which the program is executed This record is called the current record This allows us to omit the index for the record number Consider for instance the predefined subjects table This table contains one record per subject Programs in the subjects table are executed separately for each subject i e separately for each record So whenever a program is running the table and the record is fixed and therefore within a program the cell is determ ined by the variable Let us make this clear with an example Assume that a treatment is defined for three subjects The value of the variable g is 5 12 and 7 Consider now the following program 20 ML iP The program is executed for each row of the subjects table First it is executed for the first row The variables M and x are defined and get their values for the first row
126. e original file names this should not cause problems You cannot read in the file of the running session Close z Tree before separating the tables Do not use the tools while a session is running 8 6 2 Join sbj file Joins the sbj file to a file that contains a table with a column named Subject input table Joining means that the information in the sbj file i e the questionnaire data is added to each row of the input table Which line of the sbj file is entered depends on the value in the Subject column Note that the sbj file is transposed with respect to the xls file The output file will override an existing one Because the names generated are based on the original file names that should not cause problems You cannot read in the file of the running session Close z Tree before separating the tables Do not use the tools while a session is running Page 150 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Menu Commands z Tree 3 5 Tools Menu Reference Manual 8 6 3 Join files It allows you to add the lines of one table to the lines of another table based on key variables For instance you can add the data in the subjects table key table to the data of the contracts table based on the key SessionID TreatmentNumber Period Subject Data File Path of the data file If you click the label Data File a standard file
127. e position where the smiley emoticon was found First smiley occurs at character 14 Figure 3 46 String output as it appears on the client s screen 3 12 Data use across periods and treatments 3 12 1 Definition of new tables In z Tree it is possible to define more tables than the standard subjects globals summary contracts and session tables You can use these table for example for the following purposes Multiple contracts like tables for different markets Random period payment A table that contains the profits made in each period This table can cover more than one treatment Customizable history table Storing a discrete function Storing data of a payoff calculator Present different decisions in a random order To use anew table you have to define it at the beginning of the Background with the menu item Treatment New Table A dialog opens where you can enter the properties of the table Page 82 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Definition of Treatments z Tree 3 5 Data use across periods and treatments Tutorial Table Eg imj Lifetime _Lancel_ C Period Treatment r Program execution C When first subject enters stage Always when a subject enters stage C When last subject enters stage Used Variables comma separated Figure 3 47 Table dialog Lifetime If a table
128. e start of the period Its accuracy is limited to the resolution of the system timer which is typically in the range of 10 ms to 16 ms 8 3 26 New Checker Checkers are used for more complicated input checks If a condition is not met a message is displayed Condition Condition that has to be satisfied The message appears if the condition is not satisfied In contract creation boxes checkers are run for each new record In contract list boxes they are run for the selected record In all other boxes the check is carried out in the subjects table Page 128 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Menu Commands z Tree 3 5 Treatment Menu Reference Manual Message Message that appears if condition is not satisfied If there is a message box the message appears in this box Otherwise a dialog appears that needs to be confirmed by the subject yes Button Accept the input nevertheless no Button Do not accept input If there is only a yes button then the message appears and after pressing this button the input is ac cepted If there is only a no button then the message appears and after pressing this button the input is rejected If there is a yes AND a no button then the message should contain a question Pressing the yes button accepts the input pressing the no button rejects it Note on how checks are
129. e the stage 3 8 3 Auction trial periods with simulate data You plan to conduct an experiment with a double auction Because the user interface will be rather dif ficult subjects should be given some time to learn how it works This is best achieved with some trial periods A problem with trial periods is that they allow interaction between the subjects and uncontrolled learning before the actual experiment starts To allow for controlled learning you can simulate the entries of the other subjects in the trial period auctions This can be done with a sequence of later statements 3 8 4 Double auction with an external shock Suppose you want to change the economic environment during a double auction Let P be the parameter you want to change from 100 to 50 after a minute You write the following program P 100 lacer 60 clo 4 P 50 3 8 5 Exit in an ascending clock auction In an ascending clock auction the subjects are able to press a button whenever they wish to exit the auction The winner is determined when the second to last subject has exited For an auction with as cending prices we define an Exit button for subjects to exit the auction whenever they wish to do so Then we need to write a program in the subjects table into the Exit button As soon as a subject has pressed the button the button disappears ShowExitButton 0 Furthermore we need to define what happens if there is only one subject left in a group
130. e the variable Type We set it here to an illegal value and define the correct value in the parameter table To make the treatment more flexible we define the size of the pie as a variable We call this variable M The variable IncOf fer contains the increments that are allowed when making offers We allow any integer number and therefore we set this number to 1 In the Proposer offer stage we set the Participate variable so that only proposers make offers In the Responder acceptance stage we have to copy the proposer s offer into the responder s row of the subjects table We do this by defining a new variable Share It contains both subjects shares as suggested by the proposer As you can see in the formula itis M Offer for the proposer and it is the offer of the proposer for the responder To get the offer of the proposer we use the following find expression find same Group amp Type PROPOSERTYPE Offer In the Responder acceptance stage the responder can either accept or reject We use radio buttons for input i e in the Layout field of the Accept item we write radio 1 accept O reject In the Proposer profit stage we calculate the profits for both types The interesting command is in the program where we copy the Accept variable from the responder row to the proposer row Accept find same Group amp Type RESPONDERTYPE Accept Page 53 University o
131. e value in order to be able to discern that a subject has dropped out Message to the experimenter No message appears at the client s screen The experimenter sees in the state of the subject that she is making losses Page 104 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 The Stage Tree Elements z Tree 3 5 Parameter Table Reference Manual 7 3 Parameter Table 7 3 1 Period Parameters Prompt If a text is entered here it is displayed on the server before the start of the period The treatment will only continue when OK is clicked on the server Program This program is run in the globals table after the programs in the background the specific parameter program and the role program have been run 7 3 2 Role Parameters Name Of no consequence Program This program is run in the subjects table after the programs in the background and the specific parameter program have been run 7 3 3 Specific Parameters Group Group number of the subject in this period Name Of no consequence Program This program is run in the subjects table after the programs in the background have been run 7 4 Screen Background screen is being used If this field is marked the windows of the background are taken over and placed first In every stage there are two screens The active screen is shown to the subjects who participate in the stage until they have concluded the stage
132. e value value In the case of an input item it is the other way round i e if a text label is entered the variable gets the value value If text different from all labels is entered an error message appears The label text has to be in single or double quote radio value label value label Labeled radio buttons appear in a vertical order The value of the variables again corresponds to the values the labels of the buttons are the corresponding labels radiosequence value label value labelp Labeled radio buttons appear in a horizontal order The value of the variables again corresponds to the values the labels of the buttons are the corresponding labels radioline leftvalue leftlabel rightvalue rightlabel number A row of radio buttons appears They may be accompanied by labels on the left and on the right Leftvalue is the value of the button at the left margin Rightvalue is the value of the button at the right margin The value of number determines the number of buttons slider leftvalue leftlabel rightvalue rightlabel number A slider appears The slider may be accompanied by a text on the left and on the right left label is the value of the variables at the left margin right value is the value of the variables at the right margin The value of number determines the resolution i e the number of possible slider positions scrollbar leftvalue leftlabel rightvalue rightlabel
133. eation box Empty records allowed If this option is marked the subject can fill out less records than are displayed For each record however either all fields must be filled or none All records empty allowed All records can be left empty Button Position Position of button s inside the box Page 123 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Menu Commands z Tree 3 5 Treatment Menu Reference Manual Button Arrangement When the first button lies in the lower right hand corner horizontal means that further buttons are added at the left until a second row has to begin The other cases are analogous 8 3 19 New Message Box Creates a message box If there is a message box messages generated by z Tree are not displayed in separate windows This makes the restart of a client easier because in case of a restart all messages re appear too and have to be confirmed with a mouse click Initial Message Appears when the stage starts 8 3 20 New Multimedia Box In the multimedia box an image a movie or sound file can be displayed The content i e the image movie or sound of the multimedia box is stored in an external file This file must be accessible at the client s computer One way to achieve this is to put the files on a shared server and map this share to the same drive letter on each of the client computers Movies and sound are played as long as th
134. ects moving back and forth in the pages For this you use a variable CurrentPage in the subjects table which you initialize to 1 Then you create the pages for examples in container boxes Set the display condition of the first page to CurrentPage 1 the Display condition of the second page to CurrentPage 2 etc You put NEXT and PREV buttons into the boxes which contain the following programs AA NEXT IDUCCON CurrentPage CurrentPage 1 PREV button CurrentPage CurrentPag ig The programs change the variable CurrentPage and this turns the right page on and off 3 13 4 Treatments of indefinite length If you want to apply a random stopping rule the treatment will have no definite length This can be implemented in z Tree with the variable Repeat Treatment First you define a one period treatment At the end of the period you decide whether to continue the treatment or to stop This decision is written into the variable Repeat Treatment in the globals table If the variable is not defined the treatment is terminated This is the normal case If you define the variable Repeat Treatment it depends on the value of the variable whether the treatment is terminated or whether it is repeated once again If the value is smaller than or equal to zero the treatment stops If the value is greater than zero the treatment is repeated Page 86 University of Zurich Department of Economics Thurgau Institute of Economics at the Univer
135. efinition of Treatments z Tree 3 5 Simple experiments without interaction Tutorial 3 1 7 Calculation exercise Exercise The subjects have to try to calculate the sine function for a randomly determined value They are paid according to the precision of their calculation Solution In the stage tree in Figure 3 5 Solution for calculation exercise you see a solution for this experiment There are two stages In the input stage the estimation has to be made and in the profit display stage the payoff as well as other information is displayed a 4B profit display amp globals EX subjects do amp subjects Sinx round sin X 001 amp summary Diff abs Sinx Y contracts Profit 100 100 Diff session EHE Active screen fm Active screen BE Standard E Header 2D Value of x OUT X 5 B Waitingscreen E0 Your value of sinfx QUT Y a Text ED True value of sin x OUT Sinx ED Please wait until the experiment continues E0 Difference OUT Diff H 4 input stage ma X amp subjects do ED Your Payoff in this Period OUT Profit X round random pil 2 001 OK B E Active screen J Waitingscreen B E Standard ED Value of x OUT ED What is the value of sinfx IN Y 0K Waitingscreen Figure 3 5 Solution for calculation exercise The value X is a number between 0 and Yr with a precision of 001 The function random returns a uniformly
136. ems are satisfied If so the stage is concluded If there are input items then there must also be a button to conclude the input 3 1 6 The Variables Profit and TotalProfit In most economic experiments people are paid based on their decisions in the experiment In z Tree the bookkeeping of the subjects earnings is automated You only have to make sure that at the end of a period the predefined variable Profit contains the number of points a point is the experimental currency unit earned in that period At the beginning of a period Profit is always set to zero so if you do not change the variable the subjects will earn nothing During the treatment the profit is summed up in the predefined variable TotalProfit It contains the sum of the values of the Profit variable in all periods in this treatment including the current period Profit and TotalProfit are variables in the subjects table You can also display their values However you should not change the value of TotalProfit At the end of the treatment the value of TotalProfit is exchanged into the local currency unit such as CHE or The default value of the exchange rate is 1 It can be changed in the Background dialog We will explain in chapter Chapter 5 Conducting a Session how the sum of all profits can be accessed to pay the subjects Page 21 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 D
137. en There are different types of boxes In this chapter we only present the standard box Standard boxes are particularly important because they can contain items An item is a stage tree element that allows you to display an entry of a table The item dialog contains the Label field where you can enter text In the Variable field you can enter the name of a variable If a standard box contains an item then the value of the variable in the record of the subject will be displayed This value is labeled with the text in the Label field The Layout field is used to describe how the variable should be displayed For instance the number 12 can be displayed as 12 or as 12 00 In the Layout field we write the precision with which we display the variable For example it is 1 if we want to display 12 and 01 if we want to display 12 00 In the standard box items are shown in a list form The labels are right aligned and are placed to the left of the values of the variables By inserting empty items i e items with no label and no variable you can create vertical space between items If we want subjects to make an entry we also create an item To declare that input must be made we check the Input checkbox In this case we call the item an input item Other items are called output items The name entered in the Variable field is again the name of a variable in the subjects table It is not ne cessary that this variable is defined first since input items also
138. ent units at different marginal costs In this double auction the sellers produce increasing amounts of a good at decreasing marginal costs Therefore we have to define the sellers decreasing marginal costs To do so we will sort the sellers marginal costs in decreasing cost ranks and enter the goods into a table The buyers can then accept different goods units at decreasing marginal costs To do this let s go through the treatment step by step 1 We first need to create a new table in the Background with Treatment New Table for the marginal costs that contains the following variables Seller subject ID Cost costs CostRank rank of the firms marginal costs Sold 1 if sold 0 otherwise 2 Then ina program for a subjects table in the Background we create a new record marginalcosts using a new statement for all firms to calculate their costs The program looks as following Page 62 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Definition of Treatments z Tree 3 5 Posted offer markets Tutorial iE Typos marginalcosts new Firm Subject Cost 10 CostRank 1 Sold 0 marginalcosts new Firm Subject Cost 20 CostRank 2 Sold U0 This way we have assigned an increasing cost ranking for the firms costs manually Of course the rank could also be determinded using a program Add
139. ent which can easily be overlooked 3 5 2 Simultaneously in different stages In this section we show how to program a simultaneous stage Consider the example of an ultimatum game with the strategy method or any game in which different types receive different feedback for instance in the profit display In each period the subjects go through all stages one stage after the other In each stage they first arrive at the active state of the stage In this state the subjects see the active screen of this stage In the clients an window the active state of a stage is designated as The active screen is left by means of an OK button or a time out When this happens the waitingscreen appears and the subject arrives at the waiting state Wy of that stage which is designated as Whether or not the subjects can begin with the next stage depends on how the options are set in the dialog of the next stage The first of these options is the Start option It determines the precondition for the subjects to enter the stage The first two options are the options most often used Wait for all is the default If it is the value of the start option then the subjects cannot enter the stage until all subjects have finished the previous stage If the option is set to Start if possible then there is no restriction at all So as soon as a subject has finished the previous stage she can enter the stage The option Start if allows you to en
140. epartment of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Questionnaires z Tree 3 5 Making questionnaires Tutorial field Options The middle button can be separated from the others by entering a number greater than zero for Distance of central button The maximum is always the value at the right most button the minimum is the value at the left most button Maximum may therefore be smaller than minimum Radiolinelabel Label line for radio button lines Labels can be placed above the buttons at the margins The texts for this action are in the Options field Checkbox A checkbox is created for every line in the Options field These checkboxes are arranged vertically one on top of the other The resulting value is a list of all options checked Wide In the wide layout the entry region for the question appears under the label over the whole width and does not only appear on the right of the label in a second column Input This field determines whether a question is presented to the subjects input is set or whether a variable is only shown input is not set Empty allowed This is set when the question does not need to be answered Minimum Maximum Resolution When numbers have to be entered these values are used for checking With sliders scrollbars and radio lines these values are used for converting the position into a number Num rows In the wide layout for text entries this is the number of rows that
141. ermine string variables For displaying string variables the string option is not necessary You just enter the number of characters that should be displayed per line Some characters will be replaced in the output file the quote is replaced by q new line by n tab by t and back slash by Input If this checkbox is marked the subject has to enter a variable Otherwise the variable is displayed Minimum The minimum value permitted for input variables Maximum The maximum value permitted for input variables Show value value of variable or default This option appears only with input variables Normally an input field is empty in the beginning If this option is chosen the input field is filled with the current value from the database Empty allowed If this option is marked the variable may be left empty Default This option appears only with input variables If a field is left empty this value is taken as input instead Event time If this item is not empty then the corresponding variable is created in the scope of the item This variable is filled with the time of when the event on the client occured in seconds after the start of the period Its accuracy is limited to the resolution of the system timer which is typically in the range of 10 ms to 16 ms Page 131 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Menu Commands Treatment Menu Examples of
142. et a detailed description about how to deal with losses Start time of the period May contains a variable name The corresponding variable is created in the subjects table and is filled with the absolute start time of the period measured on the client as a string using the ISO 8601 notation Note that the variable will be filled not before the client entered the first stage Page 103 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 The Stage Tree Elements z Tree 3 5 The background Reference Manual Compatibility first boxes on top By default the boxes on a screen are sequentially placed on top of each other Thus the last boxes are on top Checking this box reverses this behavior which results in first boxes being on top This was the default behavior in earlier versions of z Tree Options without autoscope This option affects the processing of programs Normally autoscope is on which means that if a variable does not exist in a table the system tries to find it in the scope chain Turning autoscope off requires a stricter setting of the scope which can help detecting errors 7 2 1 Bankruptcy rules Figure 7 2 Bancruptcy rules dialog shows a screenshot of the bankruptcy rules dialog The first question appears when the subject has suffered losses that can be covered by the show up fee The second message appears when the losses suffered by the subject exceed t
143. f Konstanz 20 2 2015 Menu Commands z Tree 3 5 Treatment Menu Reference Manual 8 3 34 New Pie Plot Pie Name x center Cancel y k x radius y start angle angle line color line width p J do not draw lines to center fill color Display condition Figure 8 32 Plot pie dialog center Location of the vertex of the pie center if it is a circle or ellipse radius Vertical distance x and horizontal distance y from the center to the edge of the pie start angle In degrees The angle measure at which the pie begins angle Size of the angle do not draw lines to center If not clicked and line color size is specified the pie pieces appear with an outline Page 139 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Menu Commands z Tree 3 5 Treatment Menu Reference Manual 8 3 35 New Axis Plot Axis y ais C y ais position from to tick distance grid from to increment data label distance layout caption line color line width Display condition Figure 8 33 Plot axis dialog Name Name of the axis The name has no consequence and can serve as a comment x axis y axis Defines whether the axis is horizontal x axis or vertical y axis position Where the axis goes through For an x axis this is a y value and vice versa from
144. f Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Definition of Treatments z Tree 3 5 Continuous Auction Markets Tutorial With this line we overwrite the value in the Accept variable for both types Be cautious with overwriting you may destroy valuable data Here we do not destroy anything For the responders we overwrite the value with the old value i e we do not change it For the proposers the value of Accept had no meaning before The use of this kind of overwriting makes a program easier to read because it makes a variable that was available only for certain types available to all types in the group We place the calculation of the Participate variable into a separate program We have to use this program in two places and if we separate it we can simply copy and paste the whole program The profit display is placed into different stages for proposers and responders as they each have a dif ferent display In the two stages we set the Participate variable in such a way that only the proposers enter the proposers profit display and only the responders enter the responders profit display Finally we change the start option in the responders profit display stage to Start if possible If we omit doing this the responders only receive the profit display after the proposers have been shown their profit This creates an unnecessary delay 3 6 Continuous Auction Markets 3 6
145. for the winners Profit Prize IsWinner NumWinners 3 2 10 Example Rank dependent payment The experiment The subjects have to guess the value of a mathematical function as in Section 3 1 7 Calculation exercise but this time subjects are paid according to their relative performance The best player receives one point less than there are group members The second player receives one point less than the first and so on until the last player who receives zero points Finally we apply a cost neutral tie rule So if for instance two players have rank 2 then both get a payoff according to their average rank 2 5 In the following table we show an example In the first line we list an example of the rank In the second line we show the rank that results if we apply a tie rule that assigns the last rank in a group of players with the same rank In the last line we list the profit Rank 1 2 2 4 4 4 7 8 9 9 Bad Rank 1 3 3 6 6 6 7 8 10 10 Payment 9 7 5 75 5 5 5 3 2 5 5 Page 31 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Definition of Treatments z Tree 3 5 Symmetric simultaneous games Tutorial The solution Because only the profit display stage is different from the Section 3 1 7 Calculation exercise we show and explain only this stage B a profit display A subjects do Sinx round si
146. formatting instructions that are supported are tab tabulator par new paragraph line new line bullet bullet ql aligned to left qr aligned to right qe centered b bold b0 not bold i italic id not italic sub small and inferior numbers index super small and superior numbers exponent strike crossed through ul underline ul0d do not underline colortbl Color table See examples cfin Text color n is the index of the color table which is defined by colortbl fsn Font size n in units of half a dot The font size must be explicitly given otherwise it is larger 24 than usual in z Leaf For more complex operations it is best to format the text in a word processor and then export it as RTF However if you create the RTF code by hand it will be shorter and easier to read Examples rtf fsl18 normal font size b bold b0O no longer bold normal font size bold no longer bold Aeri alg Test i italici no longer italie ypac new Lina Text italic no longer italic new line rtf colortbl red0 green0 blue0 red128 green128 blue0 Wess One vorc imn Wene2 Glivecil the reSt alin olack Page 169 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Text Formatting z Tree 3 5 Combining RTF and inserted variables Reference Manual One word in olive the rest in black 10 3 Combining RTF and inserted variables The in
147. g M x 20 ae 12 Now the program is executed for the second row Therefore M and x get their values for the second row 20 15 12 20 8 Finally when the program is executed for the third row M and x get their values for the third row g M x 5 20 15 12 20 8 7 20 13 In this example the empty spaces signify undefined values One should not use them After a program is executed for all records of a table which is generally the case there will be no undefined cells left It s important to note that the calculation is conducted record by record not statement by statement So Mis not known for all subjects when we are calculating x for the two first subjects Page 17 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Definition of Treatments z Tree 3 5 Simple experiments without interaction Tutorial The subjects table is the most important table since it contains all the data which belongs to the subjects In many experiments it is the only table you have to work with Below we will present applications where it is more convenient or even necessary to use other tables For the moment it is sufficient if you can work with the subjects table 3 1 2 Comments In order to be able to easily understand a program days and weeks after you have worked on it you insert comments All
148. g and deactivating the trigger What What kind of event triggers the action Use on show ON if the appearance of the box should trigger the action and on hide OFF if the disappearance of the box shoud trigger the action Event time If this item is not empty then the corresponding variable is created in the scope of the corresponding box This variable is filled with the time of when the box is shown or hidden in seconds after the start of the period Its accuracy is limited to the resolution of the system timer which is typically in the range of 10 ms to 16 ms 8 3 25 New Button Input is concluded by clicking a button The labeling of the button can be defined If the text consists of an underscore _ no button appears However space for a button is kept free If the button label contains the amp character the next character is underlined If you want to insert an ampersand amp into the button label you have to duplicate it Buttons can contain checkers and programs Checkers are used for checking subjects entries Programs in buttons are executed when the button is clicked and when all checks are OK Standard boxes grid boxes and all contract boxes can contain buttons Page 127 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Menu Commands z Tree 3 5 Treatment Menu Reference Manual I No record created or selected Cancel Clear entry
149. g resolution Because the layout equals 1 the number 20 is displayed as 20 and not as 20 0 Figure 2 6 Output item dialog The second item consists of the contribution entry We will call this variable Contribution It is an input variable That means not that the value of Contribution will be displayed but the subject has to enter a value and this value is assigned to the variable Its label is Your contribution to the project It must be a multiple of 1 entered in the field Layout and between 0 and Endowment entered in Minimum and Maximum within the dialog These fields appear as soon as the check box Input is checked Your contribution to the project v IV Input Minimum jo Maximum Endowment I Show value value of variable or default IT Empty allowed m Figure 2 7 Input item dialog Page 8 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Introduction z Tree 3 5 A guided tour of a public goods experiment Tutorial The contribution entry stage will be concluded by pressing a button This button is inserted after the input item of the variable Contribution We choose Treatment New Button In the dialog that appears see Figure 2 8 Button dialog we can enter the name of the button that is displayed to the subjects In a stage where input has to be made the default OK is a good choice
150. gau Institute of Economics at the University of Konstanz 20 2 2015 Definition of Treatments z Tree 3 5 Simple experiments without interaction Tutorial 3 Definition of Treatments As explained in the introduction a treatment is a part of a session that is stored in a file In the previous chapter we gave a guided tour through the process of constructing a simple treatment In this chapter we explain in detail how to build treatments In the following sections we show how increasingly complex experiments are implemented in z Tree Each section first contains a theoretical introduction followed by examples that illustrate the concepts presented 3 1 Simple experiments without interaction In this section we present the most essential features of z Tree We first explain how data is stored in z Tree and how data is modified by programs Then we show how information is displayed to the subjects and how subjects input is processed Finally we give a first overview of how the course of action in a treatment is organized 3 1 1 Data structure and simple programming Information on the state of a session is stored in a database This database consists of tables The lines of a table are called records the columns variables Each variable has a name that identifies it The individual entries in the table are called cells By default cells contain numbers You can also store text and other kind of data into variables but all data in a column mus
151. h p z Cancel Height p E eich I left I right m Display condition F bottom Horizontal margin Vertical margin Fill color TE A __Fil coor Maintain aspect ratio x axis y axis C categorical linear logarithmic categorical linear logarithmic left 100 top 100 right 100 bottom 100 Move pointer to Figure 3 29 The canvas for a smiley face First you should insert a new plot box into the Active screen of a stage Figure 3 29 The canvas for a smiley face Make sure to check the box Maintain aspect ratio if you wish for your images not to appear distorted when you display them on different types of computer screens The smiley face shown in Figure 3 28 An on screen smiley face is made up of 3 different graphic elements a pie the yellow circle two points the eyes and 3 lines the mouth In the plot box go to the Treatment Graphics menu and insert what will be the first element of the face a new pie You can choose the angle size of the pie in our case 360 to make a full circle the location of the apex of the pie or center of the circle as well as the radius you can choose different lengths in x and y dimensions if you want to make an elliptical shape Click on Fill color to choose from a menu of colors if you do not wish to write in the rgb code directly Plot Pie Name x center eee Cancel x x y start angle angle line color line width
152. h each other and a third subject to observe the conversation We include the observer to show how chat text can be treated as both input and as output First in the Background the number of subjects should be changed to a multiple of 3 it is best to test it with several groups to make sure it works Next we will initialize several variables in the Background In the subjects table we assign groups and player ID so that there are three subjects per group and each one has a player ID of either 1 2 or 3 We use this variable to designate the observer in our case subjects with a player ID of 1 are observers The code in the subjects table can be seen in the first program in Figure 3 40 Variable initialization in the chat example Next we will initialize variables in the contracts table The variables in the contracts table Owner ID and Groupie are simply the corollaries of the subjects table variables Subject PlayerID and Group We initialize them in order to use them in the display condition of the chat box which we will explain next EE Yescksround amp globals amp subjects E summary amp contracts session amp logfile subjects do SubjectsPerGroup 3 Group roundup Subject SubjectsPerGroup 1 PlayerID mod Subject 1 SubjectsPerGroup 1 X amp contracts do Owner 0 ID 0 Groupie 0 Ie Active screen E Header B Waitingscreen Text ED Bitte warten Sie bis das Experime
153. he comment 9 1 3 Constants TRUE FALSI C 9 1 4 String definition String definitions start and end with a double quote If you want to insert double quotes use either or q Double quotes in strings are written as q This ensures that no software package that uses the file will be confused 9 1 5 Mathematical operators addition string concatenation subtraction multiplication division 9 1 6 Relational operators lt smaller lt smaller or equal equals I unequal gt greater or equal gt greater Page 154 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Programming Environment Programming language 9 1 7 Logical operators amp logical and logical or 9 1 8 Scope operators next higher scope z Tree 3 5 Reference Manual highest possible scope this is always the record of the globals table 9 1 9 Statements In the following a and b are logical expressions x y and z numeric expressions v is the name of a variable t is the name of a table s is one statement ss and sse are lists of statements x Vi if a ss if a ss else ssp if a ss elsif by SS1 elsif b gt SSo if a sso elsif b SS1 elsif b2 ssp else sse t do ss t new ss array v x array v x y l array v x y Z w
154. he own group 3 6 9 Auction stages in detail We call a stage with an automatic timeout an auction stage An auction stage forms an auction with all the following auction stages whose start option is start if possible Such an auction is started and ended simultaneously for all subjects Before the stages start all programs of these stages are executed This is necessary in order to determine which subjects will participate in which stages Example Though buyers and sellers in a double auction take part in the same auction they are shown different screens To this end we define two stages The first an auction stage for the sellers and the second an auction continuation stage for the buyers These two stages are started simultaneously the first for the sellers the second for the buyers For that we insert the following program lines into the two stages Participate if IsSeller 1 1 0 into first auction stage Participate IsBuyer into second auction stage short variant Generally auction stages are concluded when the time has run out There are two exceptions however Page 60 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Definition of Treatments z Tree 3 5 Continuous Auction Markets Tutorial If the variable AuctionStop is set to 1 in the globals table the auction is terminated immediately This is useful for example when all possib
155. he payoff also depends on the decisions of the other subjects In the terminology of z Tree this means that we need a feature to access cells in other rows than the row we are currently calculating in Table functions serve exactly that purpose In an experiment we often want more than one group to play For instance if we conduct a public goods experiment we will invite 24 subjects and we will form 6 groups of 4 subjects You can do this easily with z Tree There is also great flexibility in how groups can be matched An introduction is given in this section 3 2 1 Table functions In the public goods example we need to calculate the sum of all contributions made by all members of a group The expressions described so far always refer only to the current record In this example we need to carry out calculations over the whole table We call such calculations table functions For instance if C is the variable of the contribution then S sum C defines a new variable S which is the sum of the contributions of all subjects The variable C that appears in this expression now no longer belongs to the same record as S If i is the number of the current record then the expression above mathematically means S gt 0 j So j loops over all records Of course the argument of a table function may again be an expression This expression is then calculated for every record of the table and these results are added in the case of the sum tab
156. he show up fee The fields near yes and no contain the labeling of buttons If both buttons are not empty the user has a choice If one of the two buttons is empty the user can only confirm the given answer Depending on what button the user has clicked the action stated beside the button is executed Bankruptcy Rules x Text Do you invest your show up fee You are making losses Do you want to invest the showupfee in order to continue a yes Yes Show up fee is invested and experiment goes on no No Subject drops out Message on experimenter s screen Text Do you want to go on You are making losses Do you want to continue a yes fres Message at experimenter s screen no No C Subject drops out Message at experimenter s screen Text Please wait until the experimenter unlocks your PC Please wait until the experimenter unlocks your PC a The experimenter can either give permission to go on give a credit replace the subject exclude the subject drop out Cancel Figure 7 2 Bancruptcy rules dialog Show up fee is invested and the game continues The show up fee is used to cover the losses and the game continues The player drops out automatically OUT By putting the subject into the state OUT he or she is taken out of the game This is not wholly un problematic the programs need to be equipped for this process You can for example set an input variable to an impossibl
157. he waiting state of the current stage Page 149 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Menu Commands z Tree 3 5 Tools Menu Reference Manual 8 5 12 Stop after this period When the period that is running is finished the treatment is stopped When you have applied the command a check mark is shown in the menu You can undo it by applying it again scroll down to it and click on it Then the check mark disappears This command is particularly useful when testing a treatment 8 5 13 Restart all clients All clients are restarted For this z Tree has to know the clients addresses and the z Leaves must be accessible over the internet for instance not behind a firewall The addresses of the leaves are stored when the first treatment starts and when the command Run gt Save Client Order is applied 8 5 14 Restore Client Order Restore the clients order as it was within the previous session or after the last execution of the command Run gt Save Client Order 8 5 15 Reload Database Reloads the database i e it reloads all tables This command is used after a crashed session 8 6 Tools Menu 8 6 1 Separate Tables Reads a xls file that z Tree generated and creates new files One file per table and treatment You can select more than one file at once The output files will overwrite existing ones Because the names generated are based on th
158. hile a ss Assigns the expression y to the variable x If a returns TRUE the statements ss are executed If areturns TRUE the statements ss are executed otherwise the statements ss are executed If a returns TRUE the statements ss are executed otherwise if b returns TRUE the statements ss are executed and so on If a returns TRUE the statements ss are executed otherwise if b returns TRUE the statements ss are executed and so on If none of either the a or b statements are TRUE the statements sse are executed In the table t the statements ss are executed for all records In the table t a new record is generated and in this record the statements ss are executed Defines an array i e an indexed variable Array variables can be accessed with v x Index runs from 1 to x in steps of 1 Defines an array i e an indexed variable Array variable can be accessed with v x Index runs from x to y in steps of 1 Defines an array i e an indexed variable Array variable can be accessed with v x Index runs from x to y in steps of Z While a is TRUE the statements ss are executed Loops can be left with the key combination Ctrl Alt F5 Page 155 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Programming Environment Programming language repeat ss while a later a do ss la
159. ies simultaneously However they make their entries in different screens In z Tree every treatment is defined as a linear sequence of stages However it is not necessary for all subjects to go through all stages and it is possible that not all subjects are always in the same stage How this is achieved is explained in this section 3 5 1 Sequential moves In z Tree the variable Part icipate in the subjects table determines whether a subject enters the screens of a stage or not If this variable has a value of 1 then the subject enters that screen i e the corresponding active screen appears on the subject s screen Before the programs in a stage are executed this variable is set to 1 So if you do nothing then all subjects enter that stage If however this variable is zero then the subject does not enter the stage The subject automatically proceeds to the waiting state of that stage without seeing the screens i e the waitingscreen being shown is not replaced by the waitingscreen of the stage How can you change the value of Participate This variable is a normal variable of the subjects table and you can set it to zero or one depending on a condition In the ultimatum game example the proposers move first making an offer decision After this the re sponders decide whether or not they want to accept the offer or not Therefore we define a Proposer Decision stage and a Responder Decision stage Only the proposers go through the forme
160. in a spreadsheet program A B ICID 1 Subject V1 V2 V3 1 5 6 7 3 2 8 9 10 You would like to generate a program like if Subject Wife Waele V3 17 j if Subject 4 visa V2 9 ws l0e J This can be done using formulas in the spreadsheet program For example V1 5 can be generated using BS1 amp N amp BS2 i ua 3 3 7 Exercise General 2x2 game In this example we program a battle of the sexes game We program the example in such a way that we can use it for any two player 2x2 game Page 37 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Definition of Treatments Symmetric simultaneous games z Tree 3 5 Tutorial a BB Decision globals Active screen amp subjects E content summary ED Your choice IN Choice amp contracts i 0K session E Wattingscreen PY subjects do Ei Profit Display 4 PBC EY subjects do Payoff of a player if he plays B and the other player plays C Here we define a default OthersChoice find same Group amp not same Subject Choice Pill 0 Profit Pil2 0 if Choice 1 Pi21 0 if OthersChoice 1 Pi11 Pil2 Pi22 0 if OthersChoice 1 Pi21 Pi22 i Active screen 2 Active screen E Header Standard B Waitingscreen ED Your Choice OUT Choice B E Te
161. in blue These are the contracts for which the variable seller has the value Subject Condition Condition that determines which records are to be displayed Sorting Expressions according to which sorting is carried out separated by semi colons When sorting is to be undertaken in descending order the expression is preceded by a minus sign Example a b c sorts the columns in the following way 1 3 6 6 6 7 8 8 8 10 10 9 2 7 5 5 4 4 4 2 6 3 c 7 2 4 5 3 2 8 4 5 3 3 Scrolling After each change to the list scrolling to the beginning or to the end takes place Mark best foreign contract If no other contract is selected the contract in the direction of scrolling is automatically selected i e if scrolling has taken place towards the end the last foreign contract is chosen A contract is considered as an own contract if the owner variable has the value of the subject ID of this subject All other contracts are foreign contracts If there is no owner variable all contracts are considered as foreign Button position Position of button buttons inside the box Page 122 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Menu Commands z Tree 3 5 Treatment Menu Reference Manual Button arrangement When the first button lies in the lower right hand corner horizontal means that further buttons are added at the left un
162. in elsif if type J al dsitresia Calculak von elsif type 4 second calculation elsif type J a third calculation else Jf sou caleulat ion 3 9 2 Loops while repeat and iterator There are three forms of loops in z Tree The first is while condition statements Page 68 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Definition of Treatments z Tree 3 5 More programming if loops and arrays Tutorial zal the statements are executed and The condition is evaluated and as long as the condition returns TRU the condition is reevaluated The second is repeat statements while condition GJ x The statements are executed and then the condition is evaluated As long as the condition returns TRU the statements are executed again and the condition is reevaluated With the repeat statement the statements between the curly brackets are executed at least once Loops are frequent sources of program bugs For example if the condition in a loop never returns FALSE then the loop runs forever You can leave a loop with Ctrl Alt F5 This however results in undefined results in z Tree and should only be used when testing a treatment by the time of conducting a session there should be no more infinite loops since they are errors A third way to program loops is by using iterators An iter
163. ins the labels If the table is too long a scrollbar appears The current period appears at the end of the table The scrollbar is adjusted in such a way as to make this line visible at the beginning FF History Period a Ba T OD Period OUT Period 3 36 GO OUT a 5 0 8 OUT b Figure 3 20 History box example Container box If you place many boxes onto the screen you may lose track of things To avoid confusion you can use container boxes to structure the screen elements A container box has besides the frame no visual rep resentation on the subjects screens It only defines areas of the screen within which you can place boxes Container boxes also make it possible to define determinants of your screen layout at fewer places So if you change the layout you have to change it at relatively few places In Figure 3 21 Container box example we would like to define the width of box 1 and 2 at only one place With container boxes this is easy We define two container boxes 12 and 34 We define the width in the container box 12 and cut off the remaining box at the left Now container box 34 fills the region on the right In boxes 1 and 3 we define the heights and cut the remaining box off at the top In this way we have not entered a size spe cification at more than one place and even if we should change something the structural appearance of the screen remains the same Page 46 University of Zurich Department
164. ion is satisfied All other tables without table globals All records in the table If there is a condition the program is only executed if the condition is satisfied All other tables with table subjects globals All records in the table If the owner variable is Owner then the scope operator accesses the record in the subjects table for which Subject equals Owner This corresponds to a program in the subjects table table do if Owner Subject Ifthereisa condition the program is only executed if the condition is satisfied 9 2 2 Program in a button or in a plot item The button or the plot input item sets a scope environment It includes the globals table and the record of the subject who initiated the action e g presses the button Then it includes the record that is selected or created of the chain of record in the case of a plot input item in nested plot graphs This is the basic scope We call target table the table at the beginning of this scope chain This is for example the table in which a record is selected in a contract list box A program in the target table T is executed in this scope environment if there is no condition For all other tables X or if there is a condition in the program of the target table then the program is executed Page 163 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Programming Environment z T
165. ir standard variables 9 4 1 The subjects table The subjects table contains a record for each subject This is the main table It is freshly set up i e created anew each period The subjects table of the preceding period is available under the name OLDsubjects Values from earlier periods than the immediately preceding one are not accessible In the subjects table the variables Period Subject Group Profit TotalProfit and Participate are always defined Period Number of the period The first paying period is period 1 Thus if there are 3 trial periods the first period has the number 2 Subject Number of subject starts at 1 Group Group number as it is displayed in the parameter table possibly modified by a program Profit Profit made in this period in experimental currency units Needs to be calculated default is zero Profit is the relevant variable for payment TotalProfit Total profit made in this treatment This is calculated automatically It should not be changed Participate Indicates whether the subject is taking part in the current stage or not If Participate equals 1 he or she is taking part if 0 he or she is not taking part Default is 1 LeaveStage If set to 1 it causes a subject to leave an active state and to move to the waiting state Page 165 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Programming Environment z Tree 3 5 The table
166. isplayed in the variable column The label always appears in the left column if the variable is defined or if the variable consists only of an underscore _ If the variable is empty Page 44 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Definition of Treatments z Tree 3 5 Screen layout Tutorial the label is regarded as a title and is written centered over the whole window If the label consists of more than one line then it is aligned to the left If an item is completely empty it generates a blank line B E Standard ED Text without variables are displayed centered aa E0 shows variable a OUT a ED shows variable b DUT b shows variable a ED text in label column without variable OUT _ a0 ED please enter a value for c IN c text in label column without variable E0 OK please enter a value for c Figure 3 16 Example of the definition and the resulting layout of a standard box Text without variables are displayed centered shows variable b Grid box Like the standard box the grid box can contain items Unlike to the standard box items in a grid box are displayed in a table Each item belongs to one cell in the table If the item contains a variable this variable is displayed and labels are only used for error messages that convey to the subject in which field he or she has made a mistake If an item does not contain a variab
167. item layouts z Tree 3 5 Reference Manual Layout Input variable Output variable 2 eo radio 1 86 8 24 102 8 86 8 C 86 8 C 102 8 C 102 8 radioline 0 zero 5 five 6 zero COC oe CC Co five zero CC GCC C five radiosequence 7 seven 8 eight 9 nine C seven C eight C nine C seven eight C nine slider 0 A 100 B 101 a iB A B scrollbar 0 L 100 R 101 L a a gt R L a T gt R checkbox 1 check me T check me I checkme button 1 accept 0 reject t accepi 20 Hello World 8 3 28 New Point Plot Point I is a star not polygon Size Num vertices Start at angle from x Line color rgb 0 0 0 Line width fi Fill color OO Display condition X y Location of the center of the object is a star not polygon Connects vertices to the center rather than adjacent to each other Page 132 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Menu Commands z Tree 3 5 Treatment Menu Reference Manual Figure 8 23 Example plot points In the example on the right the checkbox is a star has been clicked on the left it hast not Size In pixels Num vertices The greater the number of vertices the rounder the object Start at angle from x Angle at which a vertex of the polygon or the star is found relative to the ce
168. itionally to the double auction as described please consider the following important aspect in this double auction Consider a firm that sells its offer In the button Sell you write a program into the subjects table that deletes every last minimal cost rank whenever the variable Sold is set to 1 The program in the subjects table is the following LowestCostRank marginalcosts minimum Firm Subject amp Sold 0 CostRank marginalcosts do if CostRank LowestCostRank amp Firm Subject amp Sold 0 cold 1 3 7 Posted offer markets In a posted offer market one market side say the sellers makes offers The other market side in our case the buyers can then one after the other select one of the offers In z Tree this seller stage is easily implemented with a normal non auction stage in which the sellers make their offers in a contract creation box The buyers select the contract in a contract list box Now to allow buyers to act sequentially we use the Number of subjects in Stage option in the stage dialog By setting it to At most one per group in stage only one subject per group may enter the stage and therefore the subjects enter the stage one after the other If nothing is specified the order in which they enter is random If the variable Priority is set the subjects with lowest value best rank enter first If a subject has to go through several stages before the next subject may enter
169. ity of Konstanz 20 2 2015 Menu Commands z Tree 3 5 Treatment Menu Reference Manual Action New This plot input must be put inside a plot box When a subject makes a new input for example clicking somewhere on the plot screen the variables named in the x y variable area are overwritten with the values of the location where the click was made Action New C Select C Drag New Table contracts v Fan xvanabe PIES y variable Figure 8 25 Options for action new of a plot input Table In which table data should be modified x variable y variable The names of the variables to be modified Action Select This plot input must be put inside an object e g a rectangle When the object is selected and released the center of the object is moved to the x y location specified unless left blank Action New C Drag Select x variable y variable Figure 8 26 Options for action select of a plot input x variable y variable The names of the variables to be modified Action Drag An object can be dragged To update an object s location a program must be inserted in the plot input Page 134 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Menu Commands z Tree 3 5 Treatment Menu Reference Manual Action C New C Select Drag Drag x y Program to calculate p Figure 8 27 Options for action drag of a plot input pO Name of the va
170. iversity of Konstanz 20 2 2015 Table of Contents z Tree 3 5 8 3 46 Matching 142 8 3 47 Utilities 144 8 3 48 Language 144 8 4 Questionnaire Menu 144 8 4 1 Info 144 8 4 2 New Address Form 144 8 4 3 New Question Form 145 8 4 4 New Ruler 145 8 4 5 New Question 145 8 4 6 New Button 147 8 4 7 Expand all 147 8 4 8 Check 147 8 4 9 Language 147 8 5 Run Menu 147 8 5 1 Clients Table 147 8 5 2 Shuffle Clients 148 8 5 3 Sort Clients 148 8 5 4 Save Client Order 148 8 5 5 Start Treatment 149 8 5 6 Start Questionnaire 149 8 5 7 tablename Table 149 8 5 8 Stop Clock 149 8 5 9 Restart Clock 149 8 5 10 Discard a client 149 8 5 11 Leave Stage 149 8 5 12 Stop after this period 150 8 5 13 Restart all clients 150 8 5 14 Restore Client Order 150 8 5 15 Reload Database 150 8 6 Tools Menu 150 8 6 1 Separate Tables 150 8 6 2 Join sbj file 150 8 6 3 Join files 151 8 6 4 Append Files 152 8 6 5 Split Files 152 8 6 6 Expand Timefile 152 8 6 7 Fix File 152 8 7 View Menu 152 Page viii University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Table of Contents z Tree 3 5 8 7 1 Treatment and questionnaire files 152 8 7 2 Toolbar 152 8 7 3 Status Ba
171. jects to proceed more quickly than the default timeout This was it Now we are done with the treatment Figure 2 9 Stage tree of the public goods experiment below shows the stage tree of our public goods treatment It is now a good time to save the treatment Choose File Save As A normal save as dialog appears You can give the treatment an appropriate name and store it in the directory you like H PG1 ztt OF x amp globals amp subjects amp summary amp contracts amp session E X subjects do EfficiencyFactor 1 6 Endowment 20 E Active screen E Header 5 Waitingscreen EA Text ED Please wait until the experiment continues B d Contribution Entry 6 Active screen Standard ED Your endowment OUT Endowment ED Your contribution to the project IN Contribution OK E Waitinascreen B Profit Display el J subjects do SumC sum same Group J Contribution N count same Group Profit Endowment Contribution EfficiencyFactor SumC N fe Active screen Standard ED Your contribution to the project OUT Contribution ED Sum of all contributions QUT SumC ED Your Income in this period OUT Profit continue E Waitinascreen Figure 2 9 Stage tree of the public goods experiment 2 3 First test of a treatment In this section we will show how to test a treatment Testing allows you to find the mistakes in a treat me
172. lay stage no entry has to be made the stage ends even if the subjects do not press the continue button When the stage ends the subjects enter the waiting screen of this stage They stay in this screen until something new happens e g a new treatment is started When you are testing a treatment you start the treatment check what was going wrong correct the errors and start the treatment again Note that while a treatment is running it cannot be modified You can stop the treatment or skip a stage during your testing for instance if you forgot to put OK buttons in any all of the stages To do so bring the client s table to the foreground and highlight the states that you want do skip In Figure 2 13 Clients table with subjects in different states you could select Contribution Entry by clicking on the corresponding field or select the whole state column by clicking into the small rectangular area on top of the state column Then select Run Leave Stage see Figure 2 14 How to skip stages for testing purposes If your treatment has multiple periods which you want to skip as well you can select Run gt Stop after this period before leaving the stages zTree Clients Table File Edit Treatment MDA Tools View Clients Table Clients Table Shuffle Clients H Sort Clients Save Client Order globals Table subjects Table contracts Table summary Table session Table logfile Tabl
173. le then the label of the item is displayed In the grid box dialog you define the number of rows and columns and the order in which the items are filled in You can fill the items column by column or row by row 5 H Grid E0 label ED input var IN b ED input var IN d second label o ovy TE E0 shows a OUT a 2D second label ED input var IN c o vov O second label 0K column by column row by row Figure 3 17 Grid box examples with column by column or row by row layout Header box In the header box period number and time are displayed as shown in the following figure All inform ation is optional and can be defined in the header box dialog Period E 4 Remaining time 5 Figure 3 18 Header box example Help box The help box displays text within a box The size of the text is not restricted to the size of the box If the help text is too long to appear in the area reserved for the help box then a scrollbar appears The help box can be labeled Page 45 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Definition of Treatments z Tree 3 5 Screen layout Tutorial Help text label A help text can explain what the subjects have to do and how a particular action can be carried out Figure 3 19 Help box example History box In a history box the results from previous periods are listed in a table A label row conta
174. le function In this way the program x sum costa DD J corresponds to the mathematical expression i cos a b j In every table function you can insert a condition as a first argument This condition is checked for every record and the table function only applies to the records that satisfy this condition Example y average a gt 0 b Page 23 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Definition of Treatments z Tree 3 5 Interactive experiments Symmetric games Tutorial Here we calculate the average of the variable b of all the subjects who have a positive variable a With the find function you get the value of a cell in another record m Pini e 12 cl e je Here a record is sought for which the variable c has the value 12 For the first record from the top that satisfies this condition the value of d eis calculated and assigned to the variable z z in the current record 3 2 2 How programs are evaluated Since each statement in a program is evaluated for all the records in a table it is important to know that programs are executed record by record and not statement by statement As long as there is no interac tion this difference does not matter However as soon as table functions are used one has to be careful To show the problem consider the following example There is a good Each subject has an endowment of the good and e
175. le into an item there is a second way to display the value of a variable It can also be inserted in text The syntax is lt variable layout gt In the output this expression is replaced by the value of the variable in the given layout Layout can be a layout command as it is defined in the Layout field of the item Of course only the number and the text options are valid For instance you cannot insert buttons in this way Variables can be inserted in labels and in the options of a layout of an item or in the text of a help box So it is for instance possible that the text of a radio button depends on what happened before in the ex periment If a text contains inserted variables it must be preceded by lt gt otherwise the text will not be processed The characters lt gt have to appear at the very beginning of the dialog field It is also possible to insert variables in the options of the layout of an inserted variable i e to nest inserted variables If a variable appears in an option of the same variable the variable name can be omitted So lt x text 1 negative 1 lt 1 gt gt is a shorter form for lt x text l negative 1 lt x 1 gt gt Be careful when you use this option for items that can change their value The width of an A item is calculated when the screen is displayed first and it is not modified afterwards So if the value of a variable changes from 1 to 20 only 2 might be displayed You
176. le sided 62 average 24 158 B background 19 bancruptcy rules dialog 104 general parameters dialog 5 103 batch file 11 box 42 common options 115 display condition 85 placement 43 button dialog 127 Page 176 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Index placement 48 questionnaire 147 C c expecon conf 95 99 calculator button box 47 dialog 117 cell 15 channel 96 char 157 chat box 78 dialog 126 checker 59 dialog 128 client 4 discard a client 149 losses 104 restart all clients 150 restore client order 150 save client order 148 shuffle clients 148 sort clients 148 clients table 95 147 clock restart 149 stop 149 code 157 command line option 171 comment 18 154 condition 33 constant 154 container box 46 dialog 118 contract creation box dialog 120 contract grid box dialog 123 contract list box dialog 121 cos 156 count 32 158 D database 15 append files 152 expand timefile 152 fix file 152 z Tree 3 5 join files 151 join sbj file 150 reload 150 separate tables 150 split files 152 division 154 do statement 28 58 155 E exp 156 experiment 4 experimenter 4 external program dialog 114 F FALSE 154 file server 4 99 find 24 158 font 173 format 158 function 156 G GameSafe 96 gamesafe export
177. le transactions are exhausted If the variable AuctionNoStop is set to 1 in the globals table the auction is not concluded even if the time is up In our example we have to set the options for the sellers and the buyers in the stage dialog For the sellers we set Wait for all in the Start group and Yes in the Leave stage after timeout group For the buyers we choose Start if possible and Yes 3 6 10 Creation of new records in the program In the contracts table new records can also be added with the new statement The syntax is table new statements New records can only be entered into the contracts table and into user defined tables The statements in curly brackets can contain initializations of the record The following example is taken from the program of the subjects table of a certain stage When a user reaches this stage a record is added in the contracts table In this record the variables Seller Buyer and Price are fixed The value Buyer is the subject ID of the subject for which the program is run contracts new Seller 1 Buyer Subject Price 25 3 6 11 Adding good properties Assume the subjects have to specify some property such as quality of the good traded after the double auction has ended If each subject trades only a known number of goods you can copy the information into the subjects table The subject can then enter this information in the subjects table for instance in an ordinary
178. les If a column does not exist in some of the input tables the value is left empty in the rows of these tables The output file will override an existing one Because the names generated are based on the original file names that should not cause problems The tools cannot be used for modifying the files of the running session Do not use the tools while a session is running 8 6 5 Split Files Splits a table into parts that can be read by old versions of Excel Should be obsolete 8 6 6 Expand Timefile Adds a data file to the time file that has been generated with the logt ime command line option in z Leaf 8 6 7 Fix File If there is a severe problem in z Tree and in some sessions the data is not correctly logged in the xls file what happens In tables which do not have a fixed number of records the contracts table or user defined tables it can happen that records are stored more than once This occurs only if there are fewer records in a later period than in an earlier period In this case it occasionally happens that the table is filled with old data Fortunately this error can easily be recognized in the file The command Tools Fix File corrects a corrupt file It also gives you a message whether there was actually an error in the file Apply this command to the xls files of sessions where you worked with the contracts table or with user defined tables that did not have a predefined number of records A te
179. lex operations it is best to format the text in a word processor and then export it as RTF However if you make the RTF code by hand it will be shorter and much easier to read Examples Iret rsig normal font size o bole OU ne longer bole normal font size bold no longer bold Page 49 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Definition of Treatments z Tree 3 5 Sequential games Tutorial Neri isle trest INi italici no longer italic par new lina Text italic no longer italic new line rtf colortbl red0 green0 blue0 red128 green128 blue0 tels One wors alin eue2 OLLvecil the rest an black One word in olive the rest in black Combining RTF and inserted variables The insertion of variables is carried out before the interpretation of RTF This makes conditional formatting possible as in the following example When the variable BOLD is 1 hallo should be shown in boldface but otherwise in plain text Zorri lt BOIMD Heese OSU pla Nid 6 ao 3 5 Sequential games In a sequential game not every subject has the same decision structure In an ultimatum game for instance only the proposers decide what to offer and only the responders accept or reject Furthermore you may want to allow simultaneous entry of these different decisions If you apply the strategy method then proposers and responders should be able to make their entr
180. ller should not have to enter the Seller variable for instance In general this subject does not even know her subject ID We want data that has no direct meaning to the subjects to be entered automatically The solution to the problem consists of a program that is placed into the button Such a program is executed when the button is pressed It is easy to write the program that sets the Buyer variable to 1 Buyer 1 But how do we set the Seller variable How can we access the ID of the subject who pressed the button The solution uses the scope operator The program in the button is executed in a scope environment When a program runs in the subjects table we can access the globals table with the scope operator Similarly if we run a program in the button of a contract creation box we can access the record of the subject who pressed the button with the scope operator A double scope operator reaches the globals table Now it is easy to set the variables Seller and Creator Seller Subject Creator Subject Note that we have to define the table in which the program should run We want to run it in the newly created record of the contracts table So in the program dialog we select the contracts table 3 6 5 Viewing offers The open offers are shown in a contract list box Such a box shows a part of the contracts table The items that are contained in the box define which columns are shown A condition defines which reco
181. lsif statement can be used It is explained in Section 3 9 1 Conditional execution of statements 3 3 2 Calculating different values for different subjects There are variables called Period and Subject that are set by z Tree Period contains the number of the current period where 1 stands for the first paid period The variable Period is defined in every table The variable Sub ject is defined in the subjects table It contains the number 1 for the first record 2 for the second and so on So the variable Subject allows you to identify each subject You can now define variables in subject or period specific terms by using these variables if Period 1 amp Subject 1 p 11 if Period 1 amp Subject y 4 p 12 gt To be precise the variable Period is defined in each table with lifetime period Lifetime of variables is explained in Section 3 12 1 Definition of new tables Page 34 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Definition of Treatments z Tree 3 5 Symmetric simultaneous games Tutorial In the next section we show how the parameter table is used to define subjects specific parameters 3 3 3 The parameter table For each treatment there is besides the stage tree a parameter table where subject specific variables may be managed In this table periods are shown in the rows and subjects in the columns tal
182. lue 52 31 then 52 4 is displayed because 52 4 is the multiple of 2 nearest to 52 31 The value of the variable can also contain a code for displaying text e g in the battle of the sexes game 1 could mean boxing and 2 could mean opera We can display these words by using a text layout In the Layout field we enter the text text 1 boxing 2 opera The exclamation mark indicates that the field does not contain simply a number or an expression that represents a number The word text is the form of output to be displayed It instructs z Leaf to display one of the words boxing or opera without the quotation marks depending on the value of the variable If the value is 1 then boxing is displayed if the value is 2 then opera is displayed To be precise if the value is closer to 1 than to 2 then boxing is displayed otherwise opera is displayed There are other options than text The radio option allows you to display radio buttons So the following layout inado tL Wisyepaline 7 2 operau displays two radio buttons labeled with boxing and with opera Depending on the value of the variable one of the two radio buttons is selected These kinds of layout options can also be used for input items For an input item with the text layout as above the input has to be entered in textual form If boxing is entered the variable gets assigned a value of 1 If opera is entered the variable gets assigned a value
183. m number smaller than the resolution of an entry to each bid BidPlusRandom Bid random 8 After having solved the problem of the ties we need to determine the maximal bid to find out which subject is awarded MaximalBid maximum BidPlusRandom j The two variables BidP lusRandom and MaximalBid must be calculated in two separate programs of the subjects table since programs are carried out completely for an entire table i e for each record of a table In our example the variable BidP lusRandom should be cal culated before the variable MaximalBid is determined to get a correct result Then the winner is Winner if MaximalBid BidPlusRandom 1 0 If you wish to keep track of winners in a table define a winnerhistory and a winner table in the Background When the subjects have made their bids the winner table needs to be updated To do this you write a new program into the subjects table for example in the stage of the profit display winners new Subject Subject NumWon winnerhistory count Winner Subject Page 39 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Definition of Treatments z Tree 3 5 Symmetric simultaneous games Tutorial Please see the reference manual for random variables Another solution to sealed bid auctions and tie breaking is explained in the next section 3 3 9 Example Private value se
184. matching groups of 12 subjects each You have to do the following 1 Set the number of groups to 4 Select the first 12 subjects in the parameter table and choose Treatment Matching gt Stranger 3 Select the last 12 subjects in the parameter table and choose Treatment Matching Stranger again 4 Choose the last 12 subjects are still selected Treatment Matching Transform In the dialog that appears select the radio button Add and enter 4 into the Value field 5 Set the number of groups to 8 8 3 47 Utilities Treatment Utilities gt Make Stage Names Unique changes the names of the stages by adding numbers in such a way that the names of the stages are unique This is important because the state of the clients is defined by the stage name 8 3 48 Language Sets the language for elements that are newly created as header boxes etc All texts within these elements can be modified later i e they can also be translated later 8 4 Questionnaire Menu 8 4 1 Info Opens a dialog in which the parameters of the selected element can be viewed and changed 8 4 2 New Address Form The address prompt asks for the subject s address The fields First Name Last Name and Continue button label are compulsory if the address form should appear The other fields are optional If the question Page 144 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2
185. ment Graphics gt New Rect In the area fill color include the variable Selected in any of the three color code areas Background 2 gbak Plot Rect amp subjects ene rr amp summary amp contracts x J0 width 50 session y fo height 50 __ Cancel amp logfile Position subjects do Selected 0 mooo Active screen waitingscreen B Stage 30 Active screen line color 100 100 x 100 100 ment m D 0 50 0 50 line width E Standard filcolor rgb 00 0 00 Selected OK E waitingscreen Picture file name P resizetofit D I centered Display condition Figure 3 36 Plot rect of the example for action select Next insert a plot input into the rectangle Make sure the plot input is within the rectangle In the Action area New is selected by default therefore change it to Select With the select option it is not necessary to fill any information in for the x and y variables Next insert a program within the plot input item The program within the subjects table should read Selected 1 Selected which will make the variable alternate between values of one and zero every time the rectangle is clicked Page 75 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Definition of Treatments z Tree 3 5 Introduction to graphics Tutorial Background P globals Plot input subjects Name OK
186. mmands z Tree 3 5 Treatment Menu Reference Manual Stranger Group matching is carried out at random for each period If a region of the parameter table is selected group matching is only carried out for this region Absolute Stranger Group matching is carried out in such a way that each subject is never in the same group with any other subject more than once This is only possible for a limited number of periods In the periods in which such a group matching is no longer possible 1 is set as group number for all subjects If a region of the parameter table is selected group matching is only carried out for this region The execution of this command can take up some time Depending on the given number it can require milliseconds minutes or days Before the command is executed a warning ap pears and you get the possibility to cancel the execution of the command Absolute Typed Stranger This creates an absolute stranger matching for heterogeneous groups If for example a group consists of a company and two employees we often do not want the same subject to have different roles This means that only those groups that contain a company and two employees are allowed The execution of this command can take up some time Depending on the given number it can require milliseconds minutes or days Before the command is executed a warning ap pears and you get the possibility to cancel the execution of the command In the following table th
187. n In this section we describe how z Tree is installed in the lab at Zurich Figure 6 1 Lab setup in Zurich shows the directory structure of the installation in Zurich leat d zLeaf exe E atee common treatments E expdata E priv E temp E testtrash P Tree experiment zee test zTree exe Figure 6 1 Lab setup in Zurich We use the command line options to tell z Tree where the files should be stored These options are xlsdir Sets the directory where the xls file is stored sbjdir Sets the directory where the subjects file is stored datadir Sets the directory where the xls and the subjectsfile are stored adrdir Sets the directory where the address file is stored paydir Sets the directory where the payment file is stored privdir Sets the directory where the address and the payment file are stored gsfdir Sets the directory where the GameSafe is stored tempdir Sets the directory where the temporary files lastclt txt db txt and prevdb txt are stored datadir Sets the directory where the treatment and questionnaire files are automatically stored before they run leafdir Sets the directory where the file server eec is stored dir Specifies a directory where z Tree put all files The shortcut zTree experiment starts z Tree with the following command line options datadir expdata leafdir zleaf privdir priv tempdir temp gsf
188. n J 001 Diff abs Sinx Y J GIS subjects do Rank count same Group amp Diff lt Diff 1 BadRank count same Group amp Diff lt Diff N count same Group J Profit N Rank BadRank 2 S Active screen E Standard E0 Value of x DUT X ED Your value of sinf OUT Y ED True value of sinf DUT Sinx DO Difference OUT Diff a0 ED Your rank OUT Rank 20 ED Your Payoff in this Period OUT Profit OK DD Waitingscreen Figure 3 8 Solution for the rank dependent payment The second program is new in this treatment The statements in this program cannot be placed into the previous program because we calculate table functions that use the variable Diff see section above Let us explain the program step by step Rank count same Group amp Diff lt Diff 1 In this line we calculate the rank The rank corresponds to the number of players who are strictly better than I am This is expressed with the condition Diff lt Diff The count table function can be read as follows We count the number of players in my group whose difference is smaller than my difference We have to add 1 because if no player is better than I am then I am first BadRank count same Group amp Diff lt Diff In this statement we count the number of players who are at least as good as I am This corresponds to the rank with the unkind tie rule N count same Group
189. n the input is not accepted In this case the condition is mandatory Since there is only a no button the subject cannot disregard the condition in the message When the checker is created it can be placed into the contract creation box as well as into the contract list box where an offer is accepted Then we create another checker for the seller side It is the improvement rule that is implemented as Price gt contracts maximum Seller 1 Price Note that it is necessary to prefix the maximum function with the name of the contracts table In the contract creation box a program as well as a condition is executed only in the new record not in the contracts table as a whole In versions earlier than 3 2 4 it was necessary to ensure that a selected offer is still available This is now automatically checked Where do the messages appear In general messages appear in anew window and the subject has to click OK in order to close the window This has the advantage that it catches the subject s attention As an alternative you can insert a message box in which the messages are displayed In this case the subject does not have to close the messages window but you risk that some subjects overlook such messages Auctions within groups If you want to conduct auctions within groups you have to set a group variable in the contracts table when you create contracts and you have to restrict the display of the recods to those in t
190. n are optional Depending on which fields have been filled the box is placed within the remaining box Figure 3 14 Box placement shows all cases for the fields width W distance to left margin L and distance to right margin R Rk L LL a a R m a Ww D m E Ww e R L M wW a L gt a ra wW sapa Figure 3 14 Box placement The Name of the box is used for documentation only In the with Frame field you define whether a line is drawn around the box If there is a frame then this frame is filled i e if you draw a box with a frame over another box then this box will be covered Otherwise it is transparent In Figure 3 15 Box placement example we show definition and placement of four boxes The first box is a header box We define a distance from the top margin of zero and a height of 10 percent The rest of the boxes should not intersect this box So we adjust the remaining box and cut the top The Page 43 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Definition of Treatments z Tree 3 5 Screen layout Tutorial second box is positioned at the left side of the remaining box with distances of 20 pixels to the margin We do not modify the remaining box Hence the third box where we define width and height is placed centrally with respect to the lower part of the screen In this box we adjust the remaining screen in a way that the b
191. n this case the variable of the item is automatically shown lt gt text ie negativen Ea ta Or Oe This also works with variables inserted in the text In the following text the value of Profit is inserted at the place of lt 0 01 gt lt o Youri prO itie SI Pror ieit ezt i Vinseeicnyele 1 we Ol Wiss If you wish to insert the symbol lt in the text the symbol should be duplicated so that it is not confused with a variable expression Be careful when you use this option for items that can change their value The width of an item is calculated when the screen is first displayed and it is not modified afterwards So if the value of a variable changes from 1 to 20 only 2 might be displayed To avoid this problem you can choose a sufficiently wide first value or place the item into a box with other items that are wider Note further that labels are evaluated only once at the beginning of the stage Variables in labels are not updated 3 4 8 Text formatting with RTF In labels of items in help boxes and in message boxes texts formatted with RTF can also be entered The RTF format begins with rtf with a blank space at the end and ends with In between is the text to which formatting instructions can be added Formatting instructions begin with and end with a blank space If a formatting option is supposed to apply only to a certain range then you can place this range in curly brackets For more comp
192. n which the variable A has the values 2 4 and 8 and the variable B has the values 5 12 and 7 After the execution of the following program the table contains the values as shown in the table below sum A BJA D sum JA 1 5 ih sum SAN wy Ble P A B C sum A B D sum A B E sum A B 2 10 48 56 114 10 24 14 48 10 10 10 30 4 12 10 48 56 114 20 48 28 96 48 48 48 144 8 7 10 48 56 114 40 96 56 192 56 56 56 168 Another intuition for the scope operator can be given by considering an example in which a table function is calculated in another table So let us consider a variable v that appears in the tables ta and tb Let us consider the expression tb sum V used in a program for table ta In this expression V is the variable V in table tb If we want to access the variable V in table ta we have to use the scope oper ator Because ta and tb are different tables it becomes more clear what the current record is Outside of the table function it is the current record in ta inside of the sum function it is the current record when we calculate the sum This record is in tb Nevertheless within the calculation of the sum as well the current record in ta can be accessed with the scope operator When we execute a table function we calculate an expression for every record of that table With every step another record becomes the
193. name For example you can start z Leaf twice once with zleaf exe name Aand once with zleaf exe name B 6 4 Running an experiment in different languages All commands in z Tree are in English Most texts for the subjects are defined by the experimenter and can therefore appear in any language The error messages in z Leaf however cannot be overridden The default language in z Tree is German the language written in Zurich You can change the language in z Tree in the menu or with command line options To change the texts in z Leaf you have to use the command line option It has the form language lan lan can have different values such as en for English or de for German see all available languages in the reference manual If you want to change the language in your environment you can create a shortcut for z Tree that initializes the language to your choice 6 5 Running more than one z Tree If you want to run more than one z Tree on one computer the different instances must use some iden tification to be distinguished from each other This distinction is called the channel The channel is set with the command line option channel ch The z Leaves and the z Tree that belong to one session must use the same channel Page 99 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Installation z Tree 3 5 A sample installation Tutorial 6 6 A sample installatio
194. ndition Figure 8 30 Plot line dialog Point 1 Point 2 x and y locations of the two points to be connected arrow size arrow width Arrow is closed a 4 EA F im a gt 5 is closed is open z Tree 3 5 Reference Manual Page 137 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Menu Commands Treatment Menu 8 3 33 New Rect Plot Rect Name x width Cancel y height Position m line color line width fled oo Picture file name I tesizetofit D 1 I centered Display condition Figure 8 31 Plot rect dialog X y Location of the object width height Size of the rectangle in units defined in the plot box Position z Tree 3 5 Reference Manual Relation of the beginning of the respective edge of the object to the location shown in x y coordinates in units determined in the plot box If left blank the rectangle is centered at the specified location Picture file name Path and name of the picture file to be shown in the rectangle Only bmp files are supported resize to fit Check this box to fit the picture into the size of the rectangle maintain aspect ratio Check this box to ensure the picture is not distorted from its original proportions centered Position picture in the center Page 138 University of Zurich Department of Economics Thurgau Institute of Economics at the University o
195. nds for the value from the table If the format of the table does not correspond with the format of the parameter table the specific parameters are filled where there is a value in the table This menu is only active when the parameter table window is in front 8 3 43 Show Variable Sets the name of a specific parameter to the value of a variable Then this value becomes visible in the parameter table This menu is only active when the parameter table window is in front 8 3 44 Append Variable Append the value of a variable to the name of a specific parameter This menu is only active when the parameter table window is in front 8 3 45 Append Text Append some text to the name of a specific parameter This menu is only active when the parameter table window is in front 8 3 46 Matching Partner A partner design for group matching is selected The first subjects constitute group 1 the next group 2 etc for each period If a range of the parameter table is selected group matching is only carried out for this region As First Selected Period Groups are matched for all periods in the same way as they are matched for the first period If a region of the parameter table is selected group matching is only carried out for this period The first period of the selection counts as the first period Page 142 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Menu Co
196. nment z Tree 3 5 The tables and their standard variables Reference Manual If another Start option is set first the first program is executed for the subject who entered first Then the second program is executed for this subject and so far When all programs for the first subject are executed then the programs for the next subjects are executed In this case not all programs are executed for all subjects The programs in the globals table are only executed for the first subject programs for the stagetree summary table only for the last one Programs in the subjects and session table are executed for the record of the subject For user defined tables it is specified in the table definition whether the program is executed at the beginning at the end or for every subject If there is an owner variable in a program of the contracts table or a user defined table the program is only executed for the records of the owner This means that it is executed for the records in which the owner variable equals the value of the given Subject variable At the beginning of each period the programs are executed in the following order Standard variables are set Programs in background Subject program in current period in the subjects table the program in the specific parameter Role program in subjects table in the role parameter Period program in globals table in the period parameter DN OT Nr Programs of the first stage 9 4 The tables and the
197. nothing happens If only one of the Page 125 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Menu Commands z Tree 3 5 Treatment Menu Reference Manual two fields is nonempty the mouse pointer is adjusted in the corresponding dimension Legal input Expression in subjects table 8 3 22 New Chat Box The chat box allows subjects to enter text into an input field and show the text as output Input is in text format and is stored in a table between quotation marks and cannot be modified The chat box is similar to a contract creation box except that input is registered by hitting the enter key rather than with a button Every time the enter key is pressed a new record is added to the selected table with the most recent text Table contracts v Input var Number of characters Number of lines Condition TRUE Output text lt gt lt 1 gt Wrap text I Output text centered Figure 8 20 Chat box dialog Table The chat box can be linked to any user defined tables as well as the contracts table Input var The variable name for the chat texts Number of characters The number of characters a subject may enter before hitting the enter key including spaces Number of lines The number of lines shown in the input text field Condition Condition that determines which records are to be displayed Output text Here you can determine what text appears
198. ns that do not represent a number but a logical value i e either true TRUE or false FALSE An example of a condition is g gt h This condition results in TRUE if and only if the variable g is at least as great as the variable h Another example the condition m n results in TRUE if and only if the variables m and n are equal Note that in contrast to the equals sign in the assignment statement the equals sign used in conditions consists of two equals signs Conditions are important because they can be used in if functions and if statements With if c x y a conditional calculation can be carried out Here x and y are normal expressions and c is a condition If c evaluates to TRUE the if expression returns the value of x otherwise it returns the value of y Because x and y can be any expression they can also contain if functions In this case we say that these if functions are nested you can of course nest any kind of function The following expression shows a nested if function that implements a profit function for a two person game in which both players can choose either 1 or 2 Profiti1l Profit12 Profit21 and Profit22 describe the payoff matrix for the subject The variable Profit21 for instance contains the payoff for the subject if the subject chooses 2 and the other subject chooses 1 Profit if Decision 1 wow Broene Jy PropitAl BOREC 22 JIP if OthersDecision 1 if Others
199. nt Most errors can also be found with a reduced number of subjects It is therefore a good strategy to try a treatment first with a reduced number of subjects because it is much easier In particular you only have to make the input for a reduced number of subjects In general it is also sufficient to try out only one period We will now test our treatment with two subjects and one period First you have to change the parameters in the Background dialog accordingly To test a treatment you have two possibilities If you work in a lab you can start z Tree and one z Leaf per subject each on a separate computer The easiest way to do this is first to start z Tree from a directory Page 10 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Introduction z Tree 3 5 First test of a treatment Tutorial on a file server and then to start z Leaf from the same network directory On each computer where you start z Leaf the starting screen of z Leaf appears If you want to test the treatment outside of the lab you can also run z Tree and several z Leaves on a single computer You just have to give the different z Leaves different names You can achieve this by creating shortcuts to zleaf exe in explorer File Create Shortcut For each shortcut you open the properties dialog click on the shortcut tab and append the text name Yourleafname to the target field see Figure 2 10
200. nt weitergeht Figure 3 40 Variable initialization in the chat example In the Active screen select Treatment New Box gt New Chat Box There is a field called Display condition as well as a field called Condition The former determines whether the box itself will be displayed or not The latter determines which rows of the contracts table or user defined table will be shown in the chat output You should insert two chat boxes one for the chatters and one for the observer Fig Page 78 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Definition of Treatments z Tree 3 5 Free form communication Strings and other Tutorial data types ure 3 41 Chat box for the chatters shows the chat box for the subjects who are allowed to chat Fig ure 3 42 Chat box for the observer shows the chat box for the observers The display condition for the chatting subjectisPlayerID 1 forthe observeritisPlayerID 1 The table is set by default to contracts which we will use In the chat box for chatters in the area Input var insert the name of the variable which you would like to represent the chat messages in our case Words In the Condition field specify which records of the contracts table should be shown In our case we wish for subjects in one group not to be able to see the other groups chat messages In the Condition field write Group Group so that
201. nter Line color In rgb Line width In pixels Fill color In rgb 8 3 29 New Plot Input Ina plot input data can be modified when subjects make a new input select an object or drag an object The action taken by the participant will trigger data to be modified if specified You can put programs into the plot inputs which will run when a subject performs the corresponding action The trigger occurs when the mouse or other trigger is released Locations all use the units determined in the plot box Nine Event r Modifiers a gp e Cancel Left click Event time Right click I Shift C Key Tr Alt Leave Stage when done C Mouse enters I Ct C Mouse leaves Use if Action New C Select Drag Figure 8 24 Plot input dialog Event What action taken by the participant should trigger an input Modifiers What modifier should be used in order for the trigger to take place Action What type of input action you are using see below for further information Event time If this item is not empty then the corresponding variable is created in the scope of the item in which the plot input lies This variable is filled with the time of when the event on the client occured in seconds after the start of the period Its accuracy is limited to the resolution of the system timer which is typically in the range of 10 ms to 16 ms Page 133 University of Zurich Department of Economics Thurgau Institute of Economics at the Univers
202. ntered or when time has run out subjects move to the waiting state of that stage and the second screen that belongs to this stage appears which is called the waitingscreen From the waiting state subjects can enter the next stage Normally subjects progress to the next stage when all subjects have reached the waiting state At the beginning of each stage calculations are carried out These calculations are defined in programs When a subject enters a stage the calculations for this subject are carried out For programs in the subjects table this means that the program is executed for the record of the subject who enters the stage Page 18 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Definition of Treatments z Tree 3 5 Simple experiments without interaction Tutorial The default procedure for how subjects proceed from stage to stage is as follows All subjects enter the first stage of the first period when the treatment is started If no input has to be made the stage is left when the button is pressed or when the timeout has expired In a stage in which input has to be made the stage is only left when the button is pressed Otherwise it could happen that an inattentive subject loses the opportunity to make the input Leaving the stage means that subjects move on to the waiting screen of the stage They can enter the next stage as soon as all subjects have left the stage
203. number A scrollbar appears The scrollbar may be accompanied by a text on the left and on the right leftvalue is the value of the variables at the left margin right value is the value of the variables at the right margin The number sets the resolution i e the number of possible scrollbar positions Jourctong Welle label p value Ieladilap Buttons appear arranged similarly to radio buttons By clicking a button the variable is set to the corresponding value Besides this each button also has the same effect as the OK button Hence at Page 130 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Menu Commands z Tree 3 5 Treatment Menu Reference Manual most one variable per screen can have the button option For output items the button option yields the same display as the text option checkbox 1 text A checkbox appears This checkbox is labeled with t ext If the box is marked it corresponds to the value 1 If it is not marked it corresponds to the value 0 Uisierenbiere A box appears in which text can be entered In contrast to the text option item input may be free text and the input is stored in a string variable The minimum and maximum field define the restric tions concerning the minimum and maximum number of characters that have to be entered The string option is more flexible than the text option allowing subjects to freely det
204. o into detail in the next chapter In this public goods treatment the subjects are matched into groups of four subjects They decide how many out of 20 points they want to contribute to a public good called the project The subjects profit is made up of two parts The first part is the amount they keep 20 minus their contribution The second part is the income from the public good All contributions in a group are summed up multiplied by 1 6 and distributed among all subjects in the group File Edit Treatment Run Tools View Untitled Treatment 1 globals subjects amp summary contracts session logfile T Active screen E Header B waitingscreen Text 0 Please wait until the experiment continues Figure 2 2 z Tree starts with one untitled treatment Let us now start programming this treatment When we start z Tree a window containing an untitled empty treatment is also opened as you can see in the figure above The treatment is represented by a tree structure called the stage tree A treatment is constructed as a sequence of stages Before we start constructing the stages we do some preparation First we set up some parameters for the treatment In the background we enter the number of subjects the number of groups the number of periods and how points earned are translated into the local currency We open this dialog either by double clicking the background element in
205. o use interactive graphics There are many possibilities for modification of graphics in addition to the typical mouse operations such as clicking and dragging objects To make graphics interactive you use the item plot input inside the plot Page 72 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Definition of Treatments z Tree 3 5 Introduction to graphics Tutorial box There are three possible actions that can occur when using a plot input which are new select and drag Action New To illustrate how the option New works we will use the smiley face from the last example In this example the left eye of the smiley will reappear wherever you click on the screen To keep track of the coordinates where the eye should be located we will give its x and y coordinates variable names In the Background insert a new program in the subjects table creating a variable called LeftEyeX and LeftEyeyY equal to 20 and 20 respectively Next replace the x and y coordinates of the left eye point with the new variable names Figure 3 33 Smiley s left eye Plot Point Name x LeftEyex er y LeftEyeY is a star not polygon Size 30 Num vertices 30 Start at angle from x 145 Line color tgb 0 0 0 Line width 1 Fill color rqb 0 00 0 00 0 00 Display condition Figure 3 33 Smiley s left eye Next inse
206. odify it You can modify any stage tree element by double clicking it or by selecting it and then choosing the menu command Treatment Info You can also move a stage tree element by selecting it and dragging it to a new place If the element cannot be moved to this new position the program will beep You can remove stage tree elements by selecting them and choosing Edit gt Cut Finally you can copy and paste an element You select the element to copy and choose Edit Copy Then you select the place where you want the element to be copied to and choose Edit Paste We are now at the end of the guided tour You can now exit the z Leaves with the Alt F4 key combination and quit z Tree with the menu command File gt Quit All data has been saved automatically In Sec tion 5 13 Data analysis we will show how to prepare the data for data analysis When you quit z Tree a dialog with the following warning will appear The session is not finished with the writing of a payment file Do you nevertheless want to quit You do not have to worry about this message This message does not mean that data has not been saved it only means that you did not create a so called payment file which is relevant when you conduct a session with real subjects This will be explained in Chapter 4 Questionnaires In the next chapter we will explain in detail how to program treatments Page 14 University of Zurich Department of Economics Thur
207. of Konstanz 20 2 2015 Questionnaires z Tree 3 5 Making questionnaires Tutorial If you have conducted an experiment where subjects played different roles for instance where there were proposers and responders then you may also want to use different questionnaires for motivational questions You can omit question forms If you want to present two different questionnaires to two dif ferent types of subjects you put the question forms for both types into one questionnaire document and omit the forms selectively for the type you want The procedure to omit question forms is similar to the procedure to omit stages in a treatment You set the variable Participate to zero if you do not want the subject to fill out that question form Since there is no subjects table available when you run a questionnaire the variable Part icipate has to be set in the session table You can do this in the program that can be entered in the question form dialog In the treatment you have to copy the type variable the variable that determines whether the subject is a proposer or a responder into the session table 4 2 3 Questions Questions in questionnaires correspond to items in treatments In items display options are defined in the field layout Here they can be set with radio buttons The fields are as follows Label Name of the question as it is shown to the subjects If no variable is set the label appears as text over the whole width of the screen V
208. offers to improve over time i e buyers must make a higher bid than the most recent highest bid Conditions such as this can be implemented by putting a stage tree element called a checker into the buttons When a button is pressed the condition in the checker is checked If the condition is not met the input can be rejected Consider first the short selling restriction meaning that the seller cannot sell goods he does not own The condition that expresses this is simply Goods gt 1 This means that the seller has at least one good to sell This expression is entered into the Condition field of the checker dialog as shown in Figure 3 27 Checker dialog xi Condition f Goods gt 1 Cancel Message You have no more goods to self This message appears if the condition is not satisfied yes Button no Button JoK Figure 3 27 Checker dialog If the check fails a message appears on the subject s screen The text of this message is You have no more goods to sell and is entered into the Message field The last two fields are the names of buttons Page 59 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Definition of Treatments z Tree 3 5 Continuous Auction Markets Tutorial of the dialog If the subject presses the yes button the input is accepted and the text appears only as a warning If the subject presses the no butto
209. omatically then you set the option to No in the option Leave stage after timeout If you want to leave the stage even if no input has been made then you enter Yes in this option If you use the Yes option in Leave stage after timeout you want to set the value of input variables to the appropriate default value 3 5 4 Example Ultimatum Game Player 1 the proposer can propose a division of a pie of 100 Let the proposal be share1 share2 Player 2 the responder can accept or reject this division If player 2 should accept this proposal then both players receive their shares If player 2 rejects then both receive nothing As shown in the following figure we define four stages for this treatment The decision of the proposers the decision of the responders the profit display of the proposers and the profit display of the responders We now go through the main steps in programming this experiment Page 52 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Definition of Treatments z Tree 3 5 Sequential games Tutorial Proposer profit globals E A subjects do amp subjects Accept find same Group amp Type RESPONDERTYPE Accept amp summary Profit if Accept 0 0 Share amp contracts iS subjects do amp session Participate if Type PROPOSERTYPE 1 0 Ei globals do i Ac
210. on OPCMP expression boolexpression BOOLFUNCTIONNAME1 I BOOLFUNCTIONNAME2 BOOLFUNCTIONNAME1R expression boolexpression boolexpression boolexpression 9 2 Scope environment When a program is executed it is always executed within a particular scope environment In the following we give a description of what environment the programs are called in 9 2 1 Program at the beginning of a stage The following table lists the scope environment for programs that are run at the beginning of a stage Table Owner Variable Scope environment Records for which the program is run globals not allowed globals The one record of the globals table If there is a condition the program is only executed if the condition is satisfied summary summary globals Record of current period If there is a condition the program is only executed if the condition is satisfied Remark To run a program in all records of the summary table use summary do in a program subjects subjects globals All records in the subjects table If the stage does not wait for all then whenever the subject enters the program is executed for the corres ponding subject session session subjects globals All records in the session table The scope operator allows accessing the corresponding record of the subjects table If there is a condition the program is only executed if the condit
211. onducting a Session 6 Installation 15 89 94 99 About z Tree z Tree 3 5 Tutorial 1 About z Tree The z Tree program was initially developed at the University of Zurich by Urs Fischbacher Now it is a joint project of the University of Zurich the Thurgau Institute of Economics and the University of Konstanz with Urs Fischbacher und Stefan Schmid working on the program It is specially designed to enable the conducting of economic experiments without much prior experience It consists on the one hand of z Tree the Zurich Toolbox for Readymade Experiments and on the other hand of z Leaf the program used by the subjects In z Tree you can define and conduct experiments You can program a broad range of experiments with z Tree including public goods games structured bargaining experiments posted offer markets or double auctions The programming of z Tree requires a certain amount of experience Thereafter the effort required for conducting experiments is minimal An experimenter with some experience in z Tree can program a public goods game in less than an hour and a double auction in less than a day On performance In Zurich z Tree has been used for almost all experiments that are conducted with computers We started with a lab containing 26 PCs with 486er processors and 16 MB RAM which are connected on an Ethernet The program always worked efficiently in this configuration For more complicated programs a good perf
212. only appear on the right of the label in a second column Input This field determines whether a question is presented to the subjects input is set or whether a variable is only shown input is not set Empty allowed This is set when the question does not need to be answered Minimum Maximum Resolution When numbers have to be entered these values are used for checking With sliders scrollbars and radio lines these values are used for converting the position into a number Num rows In the wide layout for text entries this is the number of rows that can be entered Options The labels of buttons radio buttons and in the wide layout of sliders scrollbars and radio lines Page 146 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Menu Commands z Tree 3 5 Run Menu Reference Manual Text or number Text or number radiobuttons CA CB es radiolinelabel left right ar uton A radioline CE E E E E E FE checkboxes M cc ON left tight lo Leth CCC C CCC Right i i slider p checkboxes M scrollbar al gt TN i E slider E Ue scrollbar Hes gt IR buttons _ _ S ET a Figure 8 35 Layout of questions normal layout left and wide layout right 8 4 6 New Button Buttons conclude question forms You cannot define more than one button per form However this button can be positioned anywhere on the form The label of a button can be selected at ran
213. only those records from the contracts table with a Group value equal to the Group variable from the subjects table are shown The variable Words is automatically entered as a new row to the contracts table every time the enter key is pressed Chat Box V with frame Distance to the margin p Adjustment of the remaining box Tt ol I left z E tight bottom m Width p Height p Display PlayerlD 1 condition Table contracts Input var Words Number of characters Number of lines Condition Groupie Group Output text lt gt Player lt IDI1 gt lt l 1 gt M Wrap text 7 Output text centered Figure 3 41 Chat box for the chatters Page 79 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Definition of Treatments z Tree 3 5 Free form communication Strings and other Tutorial data types Chat Box IV With frame Distance to the margin p Adjustment of the remaining box Tr Cancel r e M left Mig tight bottom Width p Height p Display PlayerlD 1 condition Table contracts x Input var Number of characters Number of lines Condition Groupie Group Output text lt gt Player lt IDI1 gt lt Words 1 gt M Wrap text 7 Output text centered Figure 3 42 Chat box for the observer However the information about group and player ID in the contracts table is not included au
214. oose Run gt Clients Table When the z Leaves connect with z Tree you see the names of the computers appear in the first column of the clients table Hn order to change the extension of a file in the Windows explorer you have to uncheck the option Hide extensions of known file types You find this option in the folder option dialog in the tab view Page 11 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Introduction z Tree 3 5 First test of a treatment Tutorial Fe chents Table TT 2 clients first second Figure 2 11 Clients Table with two clients connected As soon as enough clients are connected you can start the treatment To do this the treatment window must be in front and then you can choose Run gt Start Treatment When you have started the treatment the screen shown in Figure 2 12 Client screen of the public goods treatment appears on the computers where z Leaf runs Period Remaining time sec 25 Your endowment 20 Your contribution to the project Figure 2 12 Client screen of the public goods treatment This is the active screen of the contribution entry stage It consists of two boxes The header box at the top shows the period number as well as the time remaining Because it is contained in the active screen of the background it is shown in the active screen of each stag
215. or a questionnaire 8 1 6 Save As Saves a treatment or a questionnaire under a new name or at another place 8 1 7 Export Treatment A treatment is written in textual form in a file A treatment exported in this way may also be read in again 8 1 8 Export Questionnaire A questionnaire is written in textual form in a file A questionnaire exported in this way may also be read in again 8 1 9 Export GameSafe A GameSafe file is translated from an unreadable binary format into a gigantic ASCII file 8 1 10 Export Table A table is written in a tab separated file Page 108 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Menu Commands z Tree 3 5 Edit Menu Reference Manual 8 1 11 Import Imports a treatment or a questionnaire 8 1 12 Page Setup Not yet implemented 8 1 13 Print Not yet implemented 8 1 14 Previous files Opens a treatment or questionnaire previously used 8 1 15 Quit Quits the program A warning message appears if the session is still running i e if a treatment is running if a questionnaire is running or if the payment file is not yet written 8 2 Edit Menu 8 2 1 Undo Not yet implemented 8 2 2 Cut Deletes the marked branch in the stage tree or in the questionnaire and places it onto the clipboard 8 2 3 Copy Copies onto the clipboard the marked area of a table or the selected branch
216. or a string variable and what appears on the subject s screen Write to your partner here up to 100 characters Hello partner I m here to play the ultimatum game with you Figure 3 44 String input as it appears on the client s screen Figure 3 43 Input item for a string variable and what appears on the subject s screen shows what the input item should look like The minimum and maximum values determine the number of characters a subject is allowed to write and the layout option string allows a subject to enter text An example of what a subject may then write in can be seen on Figure 3 44 String input as it appears on the client s screen We next insert the program smileyPlace pos chat 1 into the beginning of the second stage This program counts the number of characters after which the string occurs within the string variable chat and begins counting at the character number 1 With an output item Figure 3 45 Output the position where the smiley emoticon was found we output this information to the subject Figure 3 46 String output as it appears on the client s screen Page 81 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Definition of Treatments z Tree 3 5 Data use across periods and treatments Tutorial First smiley occurs at character Variable smileyPlace Layout f1 Figure 3 45 Output th
217. orming computer helps in particular for z Tree The manual of z Tree consists of two parts the tutorial and the reference manual The tutorial can be read sequentially It starts in Chapter 2 Introduction with a guided tour in which you learn the basic elements of z Tree programming This chapter is concluded with a detailed explanation of how to set up the environment to test z Tree on a single computer In Chapter 3 Definition of Treatments you learn how to program experiments Chapter 4 Questionnaires can be omitted for the first reading Chapter 5 Conducting a Session is essential as soon as you conduct the first experiment It explains the normal procedure of an experimental session as well as how to deal with emergencies such as computer crashes Chapter 6 Installation explains how z Tree can be installed in a lab z Tree is very flexible Nevertheless it may occur that you wish to realize something that is not covered by the program On the z Tree website at http www ztree uzh ch you will find tips and tricks If you still feel something is missing or if you should find an error in the program or in the manual please send an email to ztree econ uzh ch mailto ztree econ uzh ch We would like to thank the users of z Tree for their patience with the program and for their suggestions on how to improve the program in particular Vital Anderhub Armin Falk Ernst Fehr Simon Gachter Florian Knust Oliver Kirchkamp Andreas Laschke Stefan
218. ottom part is cut The remaining box is then the rectangular area between box 1 and box 3 In the fourth box we specify no positioning Therefore it fills this remaining box It in particular inter sects box 2 The dashed line is shown here only for illustration In the actual screen the part of box 2 that is covered by box 4 is invisible Name i IV with Frame Distance to the margin p 4 r Adjustment of the remaining box Width p fo Height p Moz F le IV top r left tight I bottom 2 IV with Frame Name 0 Distance to the margin p 5 r Adjustment of the remaining box Width p p 2 Height p T top 20p I left J tight T bottom 20p Name Bl IV with Frame r Distance to the margin p 5 r Adjustment of the remaining box Width p 30 P Height p 50x T top T lett T tight M bottom Name MO O IV with Frame r Distance to the margin p Adjustment of the remaining box gt Width p Height p T top I left I tight EEA I bottom Figure 3 15 Box placement example 3 4 4 Basic box types In this section we present the basic box types In these boxes you display texts and data from the subjects table Standard box In a standard box variables of the subjects table may be displayed or entered The items are displayed from top to bottom The window is divided into a label column left and a variable column right The variables are always d
219. output items are entered in one list each record on a separate row If there is not enough space for all contracts in the list a scrollbar appears If there are input items they appear at the bottom of the list in the same layout as in a standard box When a contract list box contains a button the subject can select a record and fill in the input items When the button is clicked and the checks are OK the variables of the input items are set and the pro grams are run for the selected record It is useful for the button of a contract list box to contain a program Only with the help of a program can the contracts table be changed in such a way as to show that the contract has been selected and who has selected it Such a program could be the following Accepter Subject Accepter is a variable of the selected records Subject is the variable Subject in its own record in the subjects table For details see Chapter 9 Programming Environment on programs below On the options Table All contract boxes can be linked to any user defined table Owner var Owner variable is a variable of the contracts table The records for which the value of this variable equals the variable Subject are shown blue for each subject Example Seller is the variable in the contracts table in which the subject number of the seller is written When all sales offers are displayed on the auction screens of the sellers one can show one s own contracts
220. pFeeInvested 1 if subject agreed to invest show up fee to be able to proceed in the experiment MoneyAdded Credit limit of the subject MoneyToPay FinalProfit ShowUpFee MoneyAdded MoneyEFarned FinalProfit ShowUpFee Page 166 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Programming Environment z Tree 3 5 The tables and their standard variables Reference Manual 9 4 5 The contracts table This table is used mainly for market experiments New records can be added to this table and existing records can be changed Section 3 6 Continuous Auction Markets explains the procedure in detail Period Period in which the record was created 9 4 6 The table of the previous period OLDtables The data of past periods can be accessed in the OLD tables You just have to prefix the table name with OLD Data of even earlier periods have to be accessed indirectly or by using a table with lifetime treatment or session 9 4 7 User defined tables User defined tables can be declared at the beginning of the treatment Period Period in which the record was created Page 167 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Text Formatting z Tree 3 5 Variable output in test display Reference Manual 10 Text Formatting 10 1 Variable output in test display Besides putting a variab
221. payment file 8 5 2 Shuffle Clients Shuffles the clients at random 8 5 3 Sort Clients Sorts the clients Should names have the same beginning and a number at the end they are sorted ac cording to the value of the number at the end i e b2 comes before b11 8 5 4 Save Client Order Saves the order of the clients and how the clients can be reached over the network in order to restart them after a crash of z Tree When the first treatment is started this is done automatically The command is very useful if you have a non arbitrary assignment of types to clients It is a good practice to execute the command after the clients have been connected Page 148 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Menu Commands z Tree 3 5 Run Menu Reference Manual 8 5 5 Start Treatment Starts the treatment that is in the front window as soon as possible If it is the first treatment z Tree first checks whether the correct number of clients is connected If not a warning appears and the start can be canceled If the treatment is allowed to start z Tree waits until at least as many clients are connected with the server as are needed to run the treatment Then the treatment is started If it is not the first treatment the treatment starts immediately 8 5 6 Start Questionnaire Starts the questionnaire if this is possible A treatment needs to have been started beforehand an
222. performed First of all we always check if each field is filled The subject needs to enter a value into each field unless it is explicitly stated in the item that the field may be empty A minimum value and a maximum value need to be entered in the definition of items If a number has to be entered the resolution is also given in the layout field The subjects entries must lie between the minimum and the maximum value and it must be a multiple of the resolution If this is not the case the entry is not accepted If the label is not empty the subject receives a message telling him her which error has occurred in which field If the label is empty it bleeps and the field containing the error is marked No message appears If all these checks are passed the checkers in the button are handled 8 3 27 New Item Items are used for displaying and reading in variables An item contains the name of the variable and information on how to display it We call an item input item if the checkbox Input is checked In this case subjects have to make an entry We call an item output item if the checkbox Input is not checked In this case a variable will be displayed Items can be contained in standard boxes grid boxes history boxes and all contract boxes Like buttons items can contain checkers and programs If this is the case the item is called an active item If the item contains checkers and or programs they are invoked when the s
223. ply play on If on the other hand the subject chooses not to use the show up fee to cover his her losses he or she reaches the state BancruptShowupNo and you have to release the subject from the server If the show up fee is used and exhausted a message appears on the subject s screen informing him her that he or she has incurred a loss This message can be concluded with a question If the subject answers this question with yes he or she arrives at the state BancruptMore Yes By answering no he or she arrives at the state BancruptMoreNo In this case also the experimenter has to release the subject from the server A dialog appears by double clicking the State field There are three possibilities Page 97 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Conducting a Session z Tree 3 5 The files generated by the server Tutorial You allow the subject to continue In this case you need to type a number into the field Amount injected that is higher than the current loss You either make the subject pay this amount or alternatively consider it to be the credit limit You take it into account when ascertaining whether subjects earnings are negative However it is not shown together with the subject s profit nor is it considered in the payment file This means that you need to add the amounts injected to the amount indicated in the
224. ptions for z Tree 172 11 3 Command line options for z Leaf 173 12 The Import Format 175 Index 176 Page x University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 List of Figures z Tree 3 5 List of Figures 2 1 Client server architecture of z Tree 4 2 2 z Tree starts with one untitled treatment 5 2 3 General parameters dialog 6 2 4 Programs are entered in the program dialog 7 2 5 A stage with the active screen and the waiting screen as shown in the stage tree 7 2 6 Output item dialog 8 2 7 Input item dialog 8 2 8 Button dialog 9 2 9 Stage tree of the public goods experiment 10 2 10 Windows shortcut dialog 11 2 11 Clients Table with two clients connected 12 2 12 Client screen of the public goods treatment 12 2 13 Clients table with subjects in different states 13 2 14 How to skip stages for testing purposes 13 2 15 The warning message when leaving a stage where subjects should make input 14 3 1 The most important tables in the z Tree database 15 3 2 In the program dialog you have to specify which table the program will run in 16 3 3 Course of action 19 3 4 Input item dialog 21 3 5 Solution for calculation exercise 22 3 6 Column by column calculation 25 3 7 Solution for the guessing game 30 3 8 Solution for the rank dependent payment 32 3 9 Parameter table dialog 35 3 10
225. puterized experiment there is one or more experimenter and a number of subjects The latter communicate with one another through the experimenter In a computerized experiment this commu nication takes place through the computer The computer operated by the experimenter is called the experimenter PC The computers operated by the subjects are called subject PCs The program the exper imenter works with is called z Tree it is the server program or in short the server The program the subjects work with is called z Leaf it is the client program or in short the client client program z Leaf parameters results server program gt lt a subject PC z Tree subject s input e experimenter PC lt o gt client program z Leaf e subject PC file server Figure 2 1 Client server architecture of z Tree Be careful not to confuse the server program with the file server The latter is used to save the programs the data and the results of an experiment A file server is not mandatory for conducting an experiment since TCP IP is used for communication between z Tree and z Leaf As soon as the clients have established contact with the server communication between server and clients takes place directly not via the file server However a file server is useful for storing the experimental data and it does facilitate start up When starting z Tree can write its own IP address into a file on the file server This allo
226. r 1 Buyer 2 First with contracts do we proceed through the contracts table As in a table the scope operator allows us to access the own record In this case it is the record we have selected So the condition Buyer Buyer amp Seller 1 is satisfied for any offer of the buyer who pressed the button that is not Page 58 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Definition of Treatments z Tree 3 5 Continuous Auction Markets Tutorial yet accepted We mark these offers as deleted by setting Seller to 2 These offers then disappear from the list of open offers In general we have to put more statements into the program of an accept button We must update the stock of goods and money of the players to reflect the purchase We could for instance assume that the variables Goods and Money contain the players quantities of goods and money In this case we add the following statements to the program subjects do if Subject Buyer Goods Goods 1 Money Money Price if Subject Seller Goods Goods 1 Money Money Price oe This program ensures that the buyer receives one good and the seller receives the money 3 6 8 Checking subjects entries Often there are restrictions on the offers that can be made or accepted Incurring debts is often not al lowed Furthermore one often requires
227. r and only the responders go through the latter To this end we write the following line in a program of the subjects table in the Proposer Decision stage This is necessary because you may want to omit more than one stage In this case the change from one waiting stage to the next should be invisible to the subjects Page 50 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Definition of Treatments z Tree 3 5 Sequential games Tutorial Participate if Type PROPOSERTYPE 1 O This line sets the variable Participate If itis zero the subject does not go through this stage He or she directly reaches the waiting state of that stage without the display changing To the subject it looks as if he or she were still in a previous stage For the Responder Decision stage we use the program Participate if Type RESPONDERTYPE 1 O It is important to know that all programs at the beginning of a stage are executed for all subjects Only when all programs are finished is the variable Part icipate checked The variable Participate does not determine program execution It determines only what screens are shown Always write the participate statement in the following form iit Comenicnommomaaceziing iI O If you do not follow this convention then you always have to pay attention to the second and third arguments of the if statem
228. r since the scrollbar should not move vertically at all So yobject the y value of the object as it is being moved should be equal to ystart We do not need a program for the y value after the mouse is released since the rectangle should remain located at zero in the y dimension The x calcu lation is quite a bit more complex There are several elements included The first is the use of the minimum and maximum functions The minimum function with the format min a b returns the minimum of the two inputs a and b The maximum function has the same format and returns the maximum of the two In our example they are imbedded within one another let us first look at the min function The code to calculate xobject includes the term min RightBound RectWidth 2 xstart x xmouse This means that the rectangle should not appear beyond the scrollbar limit area xstart x is the distance between the center of the object and where it was clicked and RectWidth 2 is the distance from the center of the object to its edge Since we want that the rectangle s edge should go up to the limit line but not beyond it we allow it to be moved to the right bound making sure that it is not moved farther than the amount of space between the right edge of the rectangle and where the rectangle was Clicked The maximum function is used for the left bound It performs the corollary function of not allowing the scrollbar rectangle to move beyond the left bar xstart
229. r 153 8 8 Help Menu 153 9 Programming Environment 154 9 1 Programming language 154 9 1 1 Error handling 154 9 1 2 Comments 154 9 1 3 Constants 154 9 1 4 String definition 154 9 1 5 Mathematical operators 154 9 1 6 Relational operators 154 9 1 7 Logical operators 155 9 1 8 Scope operators 155 9 1 9 Statements 155 9 1 10 Functions 156 9 1 11 String functions 157 9 1 12 Table functions 158 9 1 13 Iterator 158 9 1 14 Syntax diagram of the programming language 159 9 2 Scope environment 163 9 2 1 Program at the beginning of a stage 163 9 2 2 Program in a button or in a plot item 163 9 2 3 Special case contract creation box 164 9 2 4 Special case multiple record creation 164 9 2 5 Summary 164 9 3 Program execution 164 9 4 The tables and their standard variables 165 9 4 1 The subjects table 165 9 4 2 The globals table 166 9 4 3 The summary table 166 9 4 4 The session table 166 9 4 5 The contracts table 167 9 4 6 The table of the previous period OLDtables 167 9 4 7 User defined tables 167 10 Text Formatting 168 Page ix University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Table of Contents z Tree 3 5 10 1 Variable output in test display 168 10 2 Formatting with RTF commands known to be processed 168 10 3 Combining RTF and inserted variables 170 11 Command Line Options 171 11 1 Command line options common for z Tree and z Leaf 171 11 2 Command line o
230. r box in the stage tree and how it is presented on z Leaf Page 118 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Menu Commands z Tree 3 5 Treatment Menu Reference Manual In the example we define six boxes the boxes 1 2 3 and 4 as well as two container boxes 12 and 34 We define the width in the container box 12 and cut off the remaining box at the left Now container box 34 fills the region on the right In boxes 1 and 3 we define the heights and cut the remaining box off at the top In this way we have not entered a size specification at more than one place and even if we should change something the appearance of the screen remains the same If we move a box from one place to another inside the stage tree it is moved after the box where the mouse button is released By moving a box over the icon of a container box it is moved into the container box and positioned at its beginning 8 3 15 New Grid Box Creates a grid box a box that shows data of the subjects table in a tabular form S A Grid E0 label eee eee ED input var IN b Sa L 0 second label OK column by column row by row Figure 8 12 Grid box examples The items are displayed in a table Each item belongs to one field If the item contains a variable this variable is displayed During checks the label is used to convey to the subject in which field he or she has made a mistake
231. r questionnaire or until you shut down the computer Therefore the final question form must not contain a button 4 2 Making questionnaires 4 2 1 Address form The address prompt asks for the subject s address The fields First Name Last Name and Continue button label are compulsory if the address form should appear The other fields are optional If the question texts in the optional fields are left empty the corresponding question does not appear on the clients screens If the fields First Name and Last Name are left empty then no form appears The payment file is written whenever the last subject has completed or passed through without completing the address form Additional variables from the session table are added to the address form if questions are placed into the address form When all subjects have passed through the address form the payment file is written This is a tab sep arated file containing computer identification earnings from the experiment and possibly names This file can be printed and payment of the subjects can be based on this list In Section 4 3 Running a questionnaire we describe how to produce individual receipts 4 2 2 Question forms Question forms consist of a list of questions The layout of the questions is adjusted with rulers All question forms except the last must contain a button Page 89 University of Zurich Department of Economics Thurgau Institute of Economics at the University
232. rays 87 4 Questionnaires 89 4 1 Overview 89 4 2 Making questionnaires 89 4 2 1 Address form 89 4 2 2 Question forms 89 4 2 3 Questions 90 4 2 4 Profit display 92 4 2 5 Rulers 92 4 2 6 Buttons 92 4 3 Running a questionnaire 92 4 4 Making individual receipts 93 5 Conducting a Session 94 5 1 Quick guide 94 5 2 Preparation of treatments and questionnaires 94 Page iv University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Table of Contents z Tree 3 5 5 3 Start up of the experimenter PC 94 5 4 The clients table 95 5 5 How a client establishes a connection with the server 95 5 5 1 How does the client know the server s address 95 5 5 2 Channel and TCP ports 96 5 6 How to fix the name of a client 96 5 7 During a session 96 5 8 Concluding a session 96 5 9 Dealing with a crashed or blocked subject PC 96 5 10 What to do if the experimenter PC crashes 97 5 11 What happens if subjects suffer losses 97 5 12 The files generated by the server 98 5 13 Data analysis 98 6 Installation 99 6 1 A simple installation with a file server 99 6 2 Installation without a file server 99 6 3 Setting up a test environment 99 6 4 Running an experiment in different languages 99 6 5 Running more than one z Tree 99 6 6 A sample installation 100 Reference Manual 101 7 The Stage Tree Elements 102 7
233. rds are displayed Since we want to show all open offers the condition is Buyer 1 Because this is an expression i e something that has a value it does not end with a semicolon The offers should be sorted according to prices Because the seller should decrease the offers over time we display decreasing prices Hence the sorting expression is Different to a program at the beginning of a stage a program in a button is not necessarily executed for all records of that database Page 57 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Definition of Treatments z Tree 3 5 Continuous Auction Markets Tutorial Price The minus sign makes the decreasing order For increasing order we do not have to use the plus sign because increasing order is the default By the way you can also interpret the order created by Price as increasing order with Price 3 6 6 Do statement As introduced in Section 3 2 5 The do statement for an auction we require a do statement With the do statement calculations can be carried out in all records of a table With do statements the program statements is executed for all records in the current table As in the table function it is possible to precede the do statement with a table name By doing this calculations are carried out in the table in question As in the table functions you may also use the scope operator here
234. ree 3 5 Program execution Reference Manual in this table X for all records satisfying the condition In this case the scope environment is the current record of the target table and the basic scope i e subject and globals table Examples There is a contract list box displaying record in the contracts table A program in the contracts table without condition has the scope environment contracts subject globals It is executed in the relevant record of the contracts table A program in the contracts table with condition has also the scope environ ment contracts subject globals but it is executed for all records satisfying the condition A program in another table has the scope environment table subject globals If you want to use the variable of the relevant record of the target table T in another table X then use a program in the target table and execute the program in the other table using the do command Owner variables are not allowed for programs in buttons and plot input items 9 2 3 Special case contract creation box The new record is not yet included in the database Thus programs in the contracts table with a condition cover only the old records 9 2 4 Special case multiple record creation In the contract creation box more than one record can be created at a time Similarly in the contract grid box a program refers to more than one record In this case programs in the target table without a con dition are execute
235. riable a a0 ED please enter a value for variable c IN c shows variable b OK text as headline please enter a value for variable c Figure 8 7 Standard box in the stage tree and how it is presented on z Leaf Variables of the subjects table may be displayed or entered The items are displayed from top to bottom The window is divided into a label column left and a variable column right The variables are always displayed in the variable column The label always appears in the left column if the variable is defined or if it consists only of an underscore _ If the variable is empty the label is regarded as title and written centered over the whole window If the label consists of more than one line it is aligned to the left Button position Buttons can be placed into corners or centered at a margin Button arrangement If more than one button is defined in this box the additional buttons can be placed either in rows or in columns If they are placed in rows z Tree first tries to fill a row starting from the corner given by the button position If the first row is full a next row is filled starting from the same comer 8 3 11 New Calculator Button Box Defines a button by which the Windows Calculator can be called up It serves as a substitute for subjects who have no calculator Figure 8 8 Calculator button 8 3 12 New History Box Creates a history box The results from previous periods are listed in a table
236. riable to indicate the location where the object is first clicked p Name of the variable to indicate the location of the mouse after clicking but before release p Name of the variable to indicate where the object should be relative to p the mouse location as the object is being dragged Program to calculate p Where the object should appear relative to where the mouse is This can either be the same as where the mouse is or be restricted for instance to allow the object to move in only one dimension e g left and right In the figure shown above the object can be dragged like a slider so only horizontally The p variable y2 is always zero whereas the p variable x2 equals x1 so the object will follow the mouse left and right but not up and down 8 3 30 New Plot Graph Plot Graph Name Table contracts X Condition TRUE Cancel Sorting Connection line color line width fill color F Fill to x axis I Connect to previous point Display condition Figure 8 28 Plot graph dialog Page 135 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Menu Commands z Tree 3 5 Treatment Menu Reference Manual Table Any custom table as well as the contracts table may be used Condition Which records should be shown in the graph Sorting Expressions according to which sorting is carried out separated by semi colons When sorting is to
237. rk them as deleted We do this by replacing the 1 in the variable Buyer by 2 Using the number 2 is somewhat arbitrary and codes an entry as deleted very simply because we have decided that 2 means deleted In this way we keep all the information about what happened during the auction In a double auction there remains one more problem If an offer is accepted we no longer know who made the offer because in such an offer both the Buyer and the Seller variables are positive We solve this problem by using a variable Creator that contains the subject ID of the subject who made the offer We could set this variable when the offer is accepted However it is more natural to set it when the offer is made Finally one should also be able to reconstruct the temporal structure in particular the sequence of offers The easiest way to achieve this is to update a counter of the number of interactions offers and acceptances in the globals table or to record the time using the function gett ime The following table summarizes the different situations that occur in a double auction The value of the variables allows us to reconstruct what happened during the auction This is not the only way to program an auction However this is very convenient It is in particular a good practice to always use the same set of variables It makes it much easier to understand your treatments Page 55 University of Zurich Department of Economics Thurga
238. rs you can hide the corresponding boxes i e for the players who cannot make offers you hide the make offer box To do so there is a display condition in the box dialog to dynamically show and hide boxes A box is shown if the condition in the display condition is empty or if the condition is satisfied The condition is calculated in the subjects table Whenever data in a subjects table changes z Leaf checks whether a box must be shown or hidden In your example the contract creation box would only appear for the group of traders who is allowed to post offers Therefore you put the condition for the group posting offers into the display condition dialog e g IsSeller 1 so that only the sellers are allowed to post offers All the groups will be able to view the contract list box if there is no restriction in the display condition dialog 2 Next you have to hide the sell button for the group that is not allowed to post offers To do this we create two different contract list boxes one with a sell button and one without a sell button Now we need to assign the boxes to the two groups of subjects sellers and buyers using the display condition In the box with the button we write in the display condition IsSeller 1 In the box without the sell button we write in the display condition IsBuyer 1 This way only the group that is allowed to post offers the sellers will be able to press the sell button How can sellers offer differ
239. rt a plot input into the plot box Make sure that the plot input is located inside the plot box and not inside any graphic item a line or point for instance Plot inputs can be put inside graphic items but this only make sense for the action options Select and Drag rather than New As shown on Figure 3 35 Stage tree of the example for action new the plot input item will trigger a program to run upon a left click of the mouse In the area New Action New of the plot input select the table subjects and enter the names of the variables which will be updated when a left click on the screen occurs Page 73 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Definition of Treatments z Tree 3 5 Introduction to graphics Tutorial Plot input Name E j r Event _ _ Modifiers _ eae Left click Right click I Shift C Key T Alt Leave Stage when done C Mouse enters T Ctl Use if Mouse leaves Action New Select C Drag New Table subjects v x variable LeftEyex yvaiable leftEyey Figure 3 34 Record mouse clicks with plot input When a click occurs on the screen the variables Left EyeX and LeftEyeyY in the subjects table will be overwritten with the location where the mouse click was released Since the subjects table has a fixed number of rows information about previous clicks on the screen will be lost
240. ry to restart the clients later It can take up to 4 minutes You can shut down and restart the experimenter PC Exiting windows and logging on again is not sufficient You can start z Tree on another computer 4 With Run gt Restore Client Order you sort the clients in the same order as they had been in the crashed session 5 With Run gt Reload database you restore all tables Since the tables are stored after each period you can restore the state when the last period was finished 6 Check how may periods have been played You find this information for instance in the summary table or in the subjects table 7 Open the treatment you were running before If n periods have been played set the number of practice periods to n minus n 8 With Run gt Start Treatment you start the treatment again 5 11 What happens if subjects suffer losses Losses by subjects can be covered by the following sources Previous profits Lump sum payment Show up fee Money injected during the session When a subject suffers losses messages appear on the screen The text of these messages is determined in the treatment in the Background If the first two sources cannot cover the losses but the show up fee can a message appears on the subject s screen It informs the subject that he or she can now choose either to use the show up fee or drop out of the game If the subject uses the show up fee he or she may sim
241. s 119 8 13 Contract creation box in the stage tree 120 8 14 Contract creation box records arranged with label s at the left hand side 120 8 15 Contract creation box records arranged with label s on top 120 8 16 Contract list box in the stage tree and how it is presented on z Leaf 121 8 17 Contract grid box in the stage tree and displayed with label on top and on the left hand side 123 8 18 Multimedia box dialog 124 8 19 Plot box dialog 125 8 20 Chat box dialog 126 8 21 On Off Trigger dialog 127 8 22 Button dialog 128 8 23 Example plot points 133 8 24 Plot input dialog 133 8 25 Options for action new of a plot input 134 8 26 Options for action select of a plot input 134 8 27 Options for action drag of a plot input 135 8 28 Plot graph dialog 135 8 29 Plot text dialog 136 8 30 Plot line dialog 137 8 31 Plot rect dialog 138 8 32 Plot pie dialog 139 8 33 Plot axis dialog 140 8 34 Absolute typed stranger matching 143 8 35 Layout of questions normal layout left and wide layout right 147 Page xiii University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 List of Tables z Tree 3 5 List of Tables 8 1 Stage options notation in stage tree view 112 Page xiv University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Tutorial 1 About z Tree 2 Introduction 3 Definition of Treatments 4 Questionnaires 5 C
242. s and their standard variables Reference Manual 9 4 2 The globals table This table contains a single record i e a single row In it values are stored that are the same for all subjects as for instance are global variables It is freshly set up i e created anew for each period The globals table of the preceding period is available under the name OLDglobals It contains the following variables per default Period As in stagetree subjects table NumPeriods ID of the last period RepeatTreatment If this variable is greater than zero after the last period the treatment is run again with the same number of periods The period counter is incremented as if it is all done in one treatment 9 4 3 The summary table The summary table contains one record per period This record is not destroyed when the period has been finished The whole table is destroyed after the treatment has been finished This table is most useful for storing and observing aggregate data of the treatment Period Number of periods as in the subjects table 9 4 4 The session table As in the subjects stagetree table this table contains one record per subject However this table is not freshly set up after each period It contains the aggregated profits earned in earlier treatments You can also use it to exchange information between treatments Subject Subject ID FinalProfit Income of the subject not including the show up fee ShowUpFee Show up fee ShowU
243. s do Right click I Shift x 0 C Key I At I Leave Stage when done LeftBound 75 C Mouse enters I Cti RightBound 75 c Use if RectiWidth 10 Mouse leaves RectHeight 10 fe Active screen Action J Waitingscreen C New C Select Stage 30 fi oe she Bred mack Program to calculate p gt r A xstart ystart xobject max LeftB ound Rectwidth 2 xstart x aera 100 fe d min RightBound Rectwidth 2 xstart x xmouse LeftBound 0 gt RightBound 0 xmouse ymouse Af LeftBound 5 gt LeftBound 5 yobject ystart A RightBound 5 gt RightBound 5 xobject yobject OF x RectWidth x 0 RectHeight 3 drag xstart ystart xmouse ymouse xobject yobject subjects do x xobject xstart x B Waitingscreen Figure 3 38 Slider example In the areas p0 p and p we can assign variable names to the associated concepts As shown in Fig ure 3 38 Slider example we name the initial location where the object is clicked xstart and ystart the location of the mouse xmouse and ymouse and the location of the object in relation to the mouse xobject and yobject Inthe bottom right field of the plot input you enter the program which determ ines where the object should be located in relation to the mouse In Figure 3 38 Slider example there are two blocks of code the first determines the x value and the second the y value The y calculation is of course simple
244. s marked the subject can fill out less records than are displayed For each record however either all fields must be filled or none In this way you can allow the subjects to offer less than the maximum possible number of contracts All records empty allowed All records can be left empty which means that no record is created Button position Position of the button the buttons in the box Button arrangement When the first button lies in the lower right hand corner horizontal means that further buttons are added on the left until one has to begin a second row The first button in the second row lies above the first button The other cases are analogous 8 3 17 New Contract List Box E Contract list 0 x OUT x GD y OUT y E0 z OUT z 0 t IN t 0 u IN u OK Figure 8 16 Contract list box in the stage tree and how it is presented on z Leaf In a contract list box a selection of records is listed Which records appear as well as the order of the re cords in the list can be set Contract list boxes are continually updated Therefore whenever a subject effects a change in the contracts table this is immediately registered and displayed in the contract list box Page 121 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Menu Commands z Tree 3 5 Treatment Menu Reference Manual The contract list box is composed as follows The values of the
245. sertion of variables is carried out before the interpretation of RTF This makes conditional formatting possible as in the following example When the variable BOLD is 1 hallo should be shown in boldface but otherwise in plain text lt gt l rti lt BOLD leescesOS Ysa Via Ve smal lao Page 170 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Command Line Options Command line options common for z Tree and z Leaf 11 Command Line Options 11 1 Command line options common for z Tree and z Leaf language lan Page 171 z Tree 3 5 Reference Manual This option sets the language as in the menu command Treatment gt Language In z Tree it concerns the default element of a treatment and questionnaire In z Leaf it is relevant for the general error messages The default value is German If you want to change this in your environment you can create a shortcut for z Tree that initializes the language of your choice In the following list we give all the options available For instance to use Finnish you can use the option language suomi Note that for the Russian and for the Ukraine version you need a Russian or Ukraine operating system Language Arabic Bahasa Indonesia Brasil Catalan Chinese Czech Danish Dutch English Finnish French German Greek Hebrew Italian Japanese Magyar Melayu Mongolian Norwegian Bokmal Norwegian N
246. sity of Konstanz 20 2 2015 Definition of Treatments z Tree 3 5 Complex move structures Tutorial If the treatment is repeated then the period counter is incremented as if there were one treatment This is implemented by modifying the number of trial periods So if you repeat a treatment with three periods the first treatment has 3 periods and no trial periods In the second run of the treatment the treatment s number of periods is changed to 6 and the number of trial periods is changed to 3 3 13 5 Example Strategy method using arrays Let us consider a treatment in which we wish to use the strategy method for a simple game subjects make decisions for all possible cases that could occur before actually knowing which one does There are two types of players A and B The A players select a number a between 1 and 10 the B players select a number b for every possible a i e they select b1 b2 b3 b10 Let the profit be the absolute difference between the two numbers a and b The formula for the calculation of profits looks something like this A fimel yoo A ales Profit if a 1 abs a bl Li a 42 alos aso2 iei 3 slos e lo3 Ne This is very long winded In such cases it is wisest to define an array i e an indexed variable In an index set every finite equidistant subset of numbers is allowed The index set needs to be defined by an array instruction before the first use of the array
247. st for this error is also included in the command Tools Separate Tables There is no problem if you use only the globals and the subjects table 8 7 View Menu 8 7 1 Treatment and questionnaire files All treatments and questionnaires opened in z Tree can be brought into the foreground in the windows menu 8 7 2 Toolbar Opens and closes the toolbar Page 152 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Menu Commands z Tree 3 5 Help Menu Reference Manual 8 7 3 Status Bar Opens and closes the status bar 8 8 Help Menu Not yet implemented Page 153 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Programming Environment z Tree 3 5 Programming language Reference Manual 9 Programming Environment 9 1 Programming language 9 1 1 Error handling There is no exception handling in z Tree You have to make sure that the parameters of a function and the arguments of operators are valid Illegal values can cause z Tree to crash 9 1 2 Comments There are two forms of comments The end line comment starts with and ends at the end of the line The other comment form starts with and ends with Comments cannot be nested but the different forms of comments ignore each other So if you use end line comments to comment your statements you can comment out the statements using t
248. t counttriggers control_register bit_to_test Instructs z Leaf to read the parallel port and record triggers from external hardware i e fMRI scanner Example counttriggers 957 5 1 tells z Leaf to check pin 12 paper out paper end bit 5 of the control register of the parallel port LPT1 957 0x03BD is the address of the control register of the parallel port LPT1 Page 173 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Command Line Options z Tree 3 5 Command line options for z Leaf Reference Manual Windows doesn t allow direct access to the parallel port Driver software has to be in stalled i e PortTalk keyfromserial port baudrate Translates input from the serial port into key presses for plot input items key event Example keyfromserial com1 19200 reads from the first serial port at 19200 baud It is currently inefficiently implemented since it polls the serial port Page 174 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 The Import Format z Tree 3 5 Reference Manual 12 The Import Format Treatments and questionnaires can be brought into a readable format with File Export This format may also be read in again This format is not described in detail here Generally however the elements of the stage tree are given a form such as the following element nam
249. t be of the same type We will present the different data types in Section 3 11 Free form communication Strings and other data types In Figure 3 1 The most important tables in the z Tree database you see a screen shot of two tables the globals table and the subjects table as they appear in an empty treatment The first row shows the names of the variables In this example the globals table contains one record and the subjects table contains 3 records When a treatment is running you can view the tables You just have to choose the table in the Run menu 3 globals table le ES C5 subjects table ioj xj in ee ee Period Subject Group otalProfit Participate daid OO f i Figure 3 1 The most important tables in the z Tree database The name of a variable can be any word To be precise a variable can be composed of letters numbers and the underscore character _ The first character of a variable must be a letter Diacritical marks blanks and punctuation marks are not allowed z Tree distinguishes between uppercase and lowercase letters so hallo Hallo and hA11o are three different variables You can give long names to variables This makes programs easier to understand If you want to give a variable a name made up of several words you can separate the words with underscores or you can begin each word with a capital letter Examples of allowed names of variables Page 15 University of Zurich Department
250. t option Start if We show how to use this option in a treatment with the following decision structure There are three players A B and C Players A and B move first then player C moves However player C only finds out the move of player A So we want to allow player C to decide as soon as player Page 84 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Definition of Treatments z Tree 3 5 Complex move structures Tutorial A has decided This would be reasonable for instance if the decision of player B were much more time consuming than the decision of player A Let Type be the variable that contains the type Let DecisionA be the input variable of player A Let DecisionB and Decisionc be the input variables of player B and C Assume that the variable must be positive so that if we initialize the variables with 1 we know who has made her entry We define 3 stages stageA stageB and stageC Additionally we assign a type value of 1 to player A 2 to player B and 3 to player C In stageA we wait for all In stageB we start immediately In stageC we start if count Type 1 amp DecisionA gt 0 count Type 1 With this condition the players C start when all players A have finished With count same Group amp Type 1 amp DecisionA gt 0 1 player C starts when her player A has finished Of course we also have to set the Participate variable
251. t the University of Konstanz 20 2 2015 Definition of Treatments z Tree 3 5 Interactive experiments Symmetric games Tutorial can achieve this by separating the two calculations into two separate programs as the part of a stage tree in Figure 3 6 Column by column calculation shows FS subjects do Value Endowment YaluePerUnit X subjects do Total alue sum Value Figure 3 6 Column by column calculation The first program is executed for all records and then the second program is executed for all the records This corresponds exactly to a column by column processing as we need it in this example There is a general rule to avoid this error Whenever you use a table function all variables used in this table function have to be defined in the stage tree above the program that contains the table function In this particular example there is also another solution which can be implemented within one program TotalValue sum Endowment ValuePerUnit 3 2 3 Table functions in other tables Table functions can also be evaluated in other tables In order to do this you simply put the name of the table followed by a dot before the table function For example if you wish to calculate the average profit of all subjects and put it into the globals table you write in a program for the globals table AvProfit subjects average Profit You can always use this notation i e you could also use
252. t the University of Konstanz 20 2 2015 Menu Commands z Tree 3 5 Treatment Menu Reference Manual Tables Names of the tables that are stored The tables have to be separated by semicolons 8 3 6 New Program In programs calculations can be carried out Programs modify the content of tables CM jj x Table subjects Owner Variable Condition PO Cancel Program a Figure 8 3 Program dialog Table The table in which the program is executed For details see Scope environment Owner Variable Allows access to a record in the subjects table with only the scope operator It is the record whose value of the Subject variable equals the value of the owner variable in this table Example You have a variable Buyer in the contracts table which contains the subject ID of the buyer By putting Buyer into the Owner Variable of the program for the contracts table you can access the record of the buyer in the subjects table just with the scope operator Condition Condition for which records the program is executed This changes the scope environment in which the program is executed See Section 9 2 Scope environment Program The program that is executed 8 3 7 New External Program Starts a windows program either on the z Tree computer or on z Leaf Condition For z Tree programs the condition is evaluated in the globals table and determines whether the program is started or not For z Leaf programs the condition is
253. tage 18 dialog 110 leave 149 start if option 84 start options 112 stage tree 20 standard box 20 44 dialog 117 statement 155 stddev 158 string literal 154 string concatenation 154 string function 157 stringtonumber 158 subject 4 bancruptcy 97 earnings 21 losses 97 profit 21 Subject 34 subtraction 154 sum 23 158 summary table 29 T table 15 dialog 112 export 108 lifetime 83 previous period 83 program execution 83 table dumper Page 179 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Index dialog 113 table function 23 158 table loader dialog 113 input file example 113 TCP port 96 TotalProfit 21 treatment export 108 import 109 new 108 open 108 save 108 start 149 stop after current period is finished 150 trial periods 66 trim 158 TRUE 154 U ultimatum game 52 upper 157 V variable 15 in text 48 168 naming 15 string 81 Ww waiting state 18 waitingscreen 18 while statement 69 155 Z z Leaf 4 z Tree 4 z Tree 3 5 Page 180 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015
254. tate of the item is changed for instance if a radio button is clicked or a slider is moved It does not work with text items i e items in which a number or text is entered with the keyboard Label Name of the variable displayed to the subjects This text may also be empty Variable Variable that is displayed or value that is read in In the case of input items only variables or array variables with a number as index are allowed For output items any expression is allowed If the variable is empty the item only displays the label If the variable contains only an underscore _ the layout is the same as when a variable has to be entered except that no value for the variable is displayed Page 129 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Menu Commands z Tree 3 5 Treatment Menu Reference Manual Layout If a number a variable or an expression is entered here the value of that field determines how the variable is rounded when it is displayed If for instance 0 2 is entered in layout and the variable contains the value 12 34 then 12 4 is displayed If it is an input item then the number is used to check whether the number entered by the subject is a multiple of this number An exclamation mark makes further formatting options available ceres valve labeli valuez ilelosllgs In the case of an output item the text label appears when the variable has th
255. tegrated into the text The example above is entered in the Label field in the following manner Simeone lt Proric oL gt PONNE The string lt gt at the beginning of the text indicates that there might be variables in the text The variable and its layout appear in smaller greater brackets separated by a vertical line In our example 0 1 is the layout The value of profit is therefore given to one decimal place The option text is also allowed as a layout This works in exactly the same way as with output items Example voun aAMeome 1s lt Wiese Vireres OS Vsimeulilvs 80 Wilkeuccpe es Page 48 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Definition of Treatments z Tree 3 5 Screen layout Tutorial Depending on whether the profit is nearer to 0 or to 80 either Your income is small or Your income is large is displayed Variables can also be inserted into the strings of the text option There you don t need to begin the string with a second lt gt If you want to define a layout in which for negative values text is written but for positive values the number to two decimal places is written you write itera ls necgaizawiel ss E Pie feistean OO det This form has the disadvantage that you also need to write the name of the variable into the Layout field However you can omit the name of the variable I
256. ter a repeat ss 9 1 10 Functions z Tree 3 5 Reference Manual The statements ss are executed Then it is checked whether ais TRUE As long as ais TRUE ss is repeated Loops can be left with the key combination Ctrl Alt F5 The expression a is calculated The resulting seconds later the statements ss are executed The statements ss are executed in the exact same scope environment in which this later com mand was called If a is negative ss is not called The expression a is calculated The resulting seconds later the statements ss are executed The statements ss are executed in the exact same scope environment in which this later com mand was called After this condition a is calculated again and a seconds later ss is executed again If a is negative the later command is cancelled At the end of the period in which this later command was started it is also cancelled In the following a and b are logical expressions x and y numeric expressions abs x and a b atan x cos x exp x gettime if a x y in x log x max x y min x y mod x y not a or a b pi power x y random randomgauss Page 156 Absolute value of x TRU E if and only if a and b are true Arctangent of x Cosine function of x Exponential of x e The number of seconds since the computer was started If a then the value of the function is x otherwise
257. ter a condition This feature is only needed for complex move structures Most experiments can be programmed with the first two options The start option allows you to define stages that are executed simultaneously Consider a two stage se quential game where the strategy method is applied i e the second mover has to make a decision for every possible choice of the first mover In this case the second and the first movers can make their decisions simultaneously We define this in z Tree as follows We define two stages one for the first mover and one for the second mover We set the Part icipate variable in the two stages so that only the first movers enter the first mover stage and only the second movers enter the second mover stage Finally we select the individual start option in the second stage So the second movers will not parti cipate in the first stage and because they do not have to wait to enter the second stage they enter the second stage essentially at the same time as the first movers enter the first stage Figure 3 24 Example Page 51 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Definition of Treatments z Tree 3 5 Sequential games Tutorial of a two stage sequential game shows this situation At the end of the stage name there is a symbol that shows the start option H first mover FS subjects do Participate iff Type FIRS
258. ter t seconds the statements are executed and then we go back to 1 There is a second form of the later statement for the situation where we want the statements to be executed at most once In this case we write later expression do statements Also in this case the expression is evaluated If the value t is negative nothing happens If the value is greater than or equal to zero then after the corresponding number of seconds pass the statements in the curly brackets are executed 3 8 2 Leaving a stage Suppose you conduct a dutch auction with multiple groups You would like the group to proceed to the next stage as soon as the good is sold You can achieve this as follows First you initialize a variable Accepted in the subjects table to 0 Then you create the later command as above You show the price in a standard box In this box there is a button and in this button you put the following program Page 65 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Definition of Treatments z Tree 3 5 Clock auctions and deferred actions Tutorial if sum same Group Accepted 0 no other player was quicker Accepted 1 subjects do 4 if same Group LeaveStage 1 The variable LeaveSt age allows you to force subjects to leave a stage In the program above all subjects in the group of the subject who accepted the price immediately leav
259. text between and as well as between and the end of the line is a comment and of no consequence for the actual running of the program i e when the program runs this text is simply ignored We will use comments in our example to explain the reasons why each statement has a particular form Examples Baile 7 liane ee b sum cos x x a there is an error in the expression in the second line therefore we put questionable parts into a comment to localize the error Comments with and may not be nested After the first occurrence of terminates the comment The following program is therefore illegal discard the following lines by putting them into a comment a first variable 1 b 2 S You may also use comments to locate errors To find an incorrect statement you can turn doubtful passages into comments until no error message appears anymore After you correct your errors you can remove the comments 3 1 3 Simple course of action A treatment consists of a number of periods This number is fixed when you run a treatment In every period a number of stages are gone through Each stage contains two screens that are shown to the subjects who are in that stage First the active screen is shown In this screen subjects can make entries or view information When the active screen of a stage is shown we also say that the subject is in the active state of that stage When data has been e
260. the sequence of stages the second and all following stages must have the and in previous stage s option set Page 63 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Definition of Treatments z Tree 3 5 Posted offer markets Tutorial 3 7 1 Example for a posted offer market In a posted offer market sellers choose prices independently and buyers cannot bargain individually but act sequentially The first come first serve principle applies for the buyers To program a posted offer market we define the stages for the sellers and the buyers separately Therefore at the beginning of a stage we put into the subjects table the condition Participate e g for the sellers Participate if IsSeller 1 1 0 Now in the buyers stage we have to make the buyers act sequentially We can do this by applying specific options in the Stage dialog To open the Stage dialog please double click the buyers stage In our example this is the stage Buy offer In the Stage dialog of the stage Buy offer we use the option Number of subjects in Stage If we do not specify this option the subjects enter the stage all together For a posted offer market however we set the option to At most one per group in stage so that only one subject per group enters the stage and therefore the subjects enter the stage one after the other The order of the subjects entries is set randomly
261. the stage tree or by first selecting this line and then choosing the menu command Treatment Info Figure 2 3 General parameters dialog shows the dialog that appears Page 5 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Introduction z Tree 3 5 A guided tour of a public goods experiment Tutorial Number of subjects Number of groups Cancel practice periods paying periods Exch rate Fr ECU Lump sum payment ECU Show up fee Fr Bankruptcy rules Start time of the period Compatibility first boxes on top Options without Autoscope Figure 2 3 General parameters dialog We set the parameters as follows The number of subjects equals 24 Because we want to define groups of 4 we will have 6 groups We have 10 repetitions and therefore we set the number of paying periods paying periods to 10 There are no trial periods and therefore we do not change the zero in the field paying periods We set the show up fee to 10 This is the amount of money that is given to the subjects just when they show up Thus it is only implemented in the first treatment In the following treatments it is ignored It is defined in the local currency unit CHF in Zurich The exchange rate defines the value of an internal point experimental currency unit in the local currency unit In our example 100 points are exchanged into 7 CHF The par
262. til a second row has to begin The other cases are analogous 8 3 18 New Contract Grid Box 5 Contract table E0 x OUT x E0 y OUT y E0 z OUT 2z ED t IN t OK records in rows records in columns Figure 8 17 Contract grid box in the stage tree and displayed with label on top and on the left hand side The selected records are shown in a table Values of the output items and input fields for the input items appear in this table There must be space for all contracts in the table This box works similarly to the standard box except that variables from the contracts table not from the subjects table can be viewed and changed in it The images above show contract grid boxes On the left the records are displayed in rows and on the right in columns On the options Table All contract boxes can be linked to any user defined table Owner variable The owner variable is a variable in the contracts table For each subject the records for which this variable has the same value as the variable Subject are shown in blue Condition Condition for the records that are displayed The expression in this field is evaluated for each record Those records are shown for which the value of the condition is TRUE Sorting Expressions according to which sorting is carried out separated by a semi colon If sorting is to be carried out in descending order the expression is preceded by a minus sign Records display As in the contract cr
263. tive screen PROPOSERTYPE 1 ic Standard RESPONDERTYPE 2 E0 Your offer OUT Offer A a subjects do ED lt gt Your offer was lt Accept ltext 1 accepted O tejeced gt Type 0 a M 100 ED Your income in this period OUT Profit IncOffer 1 ma i Active screen E continue E Header T Waitingscreen S T Waitingscreen it B Responder profit Text Ei subjects do ED Please wait until the experiment continues Participate if Type RESPONDERTYPE 1 0 Proposer offer i Active screen el a subjects do B E Standard Participate if Type PROPOSERTYPE 1 0 ED The offer you received OUT Share rl E Active screen ED lt gt You lt Accept Iltext 1 accepted O tejeced gt this offer B E Standard oo ED Your offer IN Offer ED Your income in this period OUT Profit OK fn E Waitingscreen E continue o Responder acceptance E Waitingscreen el X subjects do Participate if Type RESPONDERTYPE 1 0 subjects do Share if Type PROPOSERTYPE M Offer find same Group amp Type PROPOSERTYPE Offer i Active screen Standard ED The offer is QUT Share E0 Do you want to accept or to rejects this offer IN Accept OK E Waitinascreen Figure 3 25 Example of an ultimatum game First we define the constants PROPOSERTYPE and RESPONDERTYPE We use these constants as names for the numbers 1 and 2 Then we defin
264. to For an x axis it defines left and right borders for a y axis it defines bottom and top border tick distance Distance between ticks The first tick is drawn at the from position If the tick should start in the middle use two axes grid from to increment Allows to draw a set of lines vertically to the axis data label distance layout Distance between labels that display the value of the axis The layout has the same format as the item captions Text that is displayed close to the axis If you do not like the placing use a plot text instead line color line width Color and width of all lines of an axis This includes ticks and grid lines Use more than one plot axis if you want to differentiate Display condition Condition whether the axis is shown or not Page 140 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Menu Commands z Tree 3 5 Treatment Menu Reference Manual 8 3 36 Slide sequence Defines a sequence of slides based on the records of a table Variables in elements within the slide sequence have access to the variables of the records of the slide sequence As plot graphs slide sequences can be nested If nested the scope environment is set up as in the case of the plot graph Name Name of the slide sequence Table Any custom table as well as the contracts table may be used Condition Which records should be shown in the slide sequence Sorting
265. tomatically so we can include a program within the chat box to enter this information In the chat box enter a new program and change the table to contracts Enter the code shown below to keep track of group subject ID and player number within the group Subject Subject Group Group ID PlayerID Each time the enter key is pressed the new row of the contracts table will be modified to include this information So in addition to using the group variable in the Condition field we can use the player ID variable in the output text This is where you can enter what text variable appears The syntax lt gt lt 1 gt appears by default in the Output text field If you leave this blank and there is an input variable the input variable will automatically be shown as output If there is no input as it is the case for the observer you must include the variable In the Output text field of the observer s chat box writing lt gt lt Words 1 gt will allow the observer to see the chats of the members of her group As in any chat situation it is useful to know who is saying what So we will imbed the player ID in the output text The Output text field should then appear as lt gt Player lt ID 1 gt lt Words 1 gt which allows the participants to see the player ID in front of each chat message The lt gt symbols are used when a variable included within text will occur In the code shown above we include two variables ID an
266. u Institute of Economics at the University of Konstanz 20 2 2015 Definition of Treatments z Tree 3 5 Continuous Auction Markets Tutorial Seller Buyer Creator Price Open offer of seller ID of seller 1 ID of seller Offer Accepted offer of seller ID of seller ID of buyer ID of seller Offer Trading price Offer of seller that is no ID of seller 2 ID of seller Offer longer valid Open offer of buyer 1 ID of buyer ID of buyer Offer Accepted offer of buyer ID of seller ID of buyer ID of buyer Offer Trading price Offer of buyer that is no 2 ID of buyer ID of buyer Offer longer valid 3 6 3 Preparing the layout for the auction Before we start to define the boxes let us discuss the layout Because the layout of sellers and buyers are very similar we only discuss the layout for the buyer The buyer can make offers he can view the offers of the other buyers and in a third box he can view the offers of the sellers and accept them We will arrange the screen as shown in Figure 3 26 Sketch of box arrangement for an auction Your offer Box for making offers Make offer Figure 3 26 Sketch of box arrangement for an auction Buyer offers List with buyers offers higher better offers are positioned downwards Seller offers List with sellers offers lower better offers are positioned upwards Accept offer The box for making the
267. ue H guess 30 ED You won 1 you won 0 you did not OUT IsWinner a 5 Active screen ED Number of winners OUT NumWinners B E Standard m a E0 Your guess IN Guess 2D Your income OUT Profit OK E continue E waitingscreen waitingscreen Figure 3 7 Solution for the guessing game In the Background we define the constants as usual In the first stage the subjects enter their guesses In the second stage we perform the calculations Let us explain each step of the calculations The group average is calculated with the table function average GroupAverage average same Group Guess The value to guess called Target Value is just the product of the average and the factor of 7 TargetValue GroupAverage Factor The relevant difference is the absolute value of the difference between the guess and the value to guess Diff abs Guess TargetValue The smallest difference called BestDiff is the minimum of all differences BestDiff minimum same Group Diff Page 30 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Definition of Treatments z Tree 3 5 Interactive experiments Symmetric games Tutorial As we have explained above it is important that this table function is placed into a new program Pro grams are executed row by row So if we were to place the calculation of BestDiff into the same program as the cal
268. using the Cut command Ctrl X but not with the delete key Delete 7 1 4 Moving elements Elements and branches can be moved with the mouse When it is ambiguous whether an element is moved after or within an element then moving the element onto the icon moves it after the element if it is moved onto the text it is moved into the element 7 1 5 Editing elements The parameters of stage tree elements are edited in the dialog The dialog can be opened using the Treatment Info menu command or with a double click 7 2 The background Information not specific for a particular stage may be inserted and defined in the Background First the background contains a list of tables that are used for calculations Then in the screens of the background elements can be placed that are used in all stages In our example all active screens have a header window and all waiting screens a text Please wait until the game continues The programs of the background are run at the beginning of a period They are used for defining constants In the background itself i e when you double click it some central parameters of the treatments can be viewed and changed Page 102 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 The Stage Tree Elements z Tree 3 5 The background Reference Manual Number of subjects K Number of groups Cancel practice periods paying periods
269. variable For the moment think of a program in the globals table The most important element in a program is the assignment statement It does a calculation and assigns the result of this calculation to a variable The syntax of the assignment is the following Name_of_variable expression The expression on the right side of the equation is calculated and assigned to the variable on the left side Note that each assignment statement is concluded with a semi colon If this variable already has a value this value is overridden If the variable does not yet exist then it is created by this statement All basic kinds of calculation are permitted in an expression As usual multiplication and division are calculated before addition and subtraction In all other cases you calculate from left to right Thus 2 3 4 makes 14 not 20 and 10 5 2 makes 3 not 7 If you want to change the order of calculation you have to use brackets A series of functions is furthermore available such as min max exp random and round The reference manual includes a complete list of all operators and functions that an expression can contain All variables used in an expression must have been created previously i e they must be defined Page 16 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Definition of Treatments z Tree 3 5 Simple experiments without interaction Tutorial in the program abov
270. wish By double clicking you can view and change the parameters of the elements Besides this the elements may be moved and copied You can insert new elements with menu commands New elements are placed either after the selected element on the same level or at the first position within the selected element This means for instance that you have to select the preceding stage to insert a new stage if you have selected the Waitingscreen element you will not be able to insert anew stage because a stage cannot be placed at the same or at a lower level of a screen There are two in relations in the stage tree A stage tree element x can contain other elements y i e the elements y are placed within the element x For instance a program is contained in a stage On the other hand the properties of the element x are also within x they can be found by double clicking the element To make this difference more clear we will use the within relation only for the elements and not for the properties i e we will say that the elements y are within x For the parameters we do not use the in metaphor we will say at most that a property of x is defined within the dialog of x For instance the name of the stage is defined in the stage dialog 3 1 5 Data display und data input The screen layout determines what data is displayed and what data input has to be made by the subjects Screens consist of boxes rectangular areas of the scre
271. wn until the subject can continue Contribution Entry m Active screen Fj Waitingscreen Figure 2 5 A stage with the active screen and the waiting screen as shown in the stage tree Now we define the Active screen of the Contribution Entry stage A screen consists of boxes rectangular parts of the screen There are different kinds of boxes which all can be created from the hierarchical menu Treatment New box The most common box is the standard box To create a box we select the Active screen element in the Contribution Entry stage and choose Treatment New box New Standard box In the dialog that appears all options are already set properly So we conclude the dialog with a click on the OK button Into this box we place items An item is the representation of a variable First we show the endowment variable Endowment We select the Standard box and choose Treatment gt New item We put Your endowment into the field Label Endowment into the field Variable and 1 into the field Layout This means that the variable Endowment will be shown labeled with the text Page 7 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Introduction z Tree 3 5 A guided tour of a public goods experiment Tutorial Your endowment The layout determines how the variable is displayed If it is a number it means that the number has the correspondin
272. ws the clients to find out which computer the server was started on This makes it easily possible to use different computers as experimenter PCs without having to inform the clients explicitly By session we mean the events that occur in the time span between the arrival of the subjects and the moment they have received payment A set of corresponding sessions constitutes an experiment A treatment is a part of a session The definition of each treatment is stored in one file A treatment is a type of z Tree document How treatments are defined is explained in Chapter 3 Definition of Treatments Each session consists of one or more treatments and questionnaires Questionnaires are also a type of z Tree document and can be freely defined Questionnaires will be explained in Chapter 4 Questionnaires Page 4 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Introduction z Tree 3 5 A guided tour of a public goods experiment Tutorial In Section 2 2 A guided tour of a public goods experiment and Section 2 3 First test of a treatment we make a guided tour through the definition of a treatment The purpose of these sections is to get a first impression of how to program with z Tree 2 2 A guided tour of a public goods experiment In this section we go through the programming of a simple public goods treatment We will present the programming on an intuitive level and g
273. x gt k T RecWidth 2 xstart x Figure 3 39 Slider handle calculations Page 77 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Definition of Treatments z Tree 3 5 Free form communication Strings and other Tutorial data types The last piece of code is found in the program below the drag item It updates the value of x subtracting the distance from the center of the object to the location where it was clicked So as shown in Figure 3 38 Slider example the program should read x xobject xstart x 3 11 Free form communication Strings and other data types Since z Tree version 3 4 strings can be used in every item Thus a chat function can also be implemented using standard elements In this section we will first demonstrate how to implement a chat treatment using a chat box It is useful because it integrates all the functions necessary for a chat In addition it allows messages to be finished with the return key and it provides an output format that is particularly useful for chats 3 11 1 The chat box The chat box allows controlled communication between subjects and it uses the contracts table or a user defined table Subjects see a text entry field and when they press the enter key on the keyboard the text is stored as a new entry in the contracts or user defined table In this example we will allow two subjects to chat wit
274. x for selecting an offer 3 6 2 A double auction in the contracts table In an auction the records of the contracts table contain the offers made by sellers and buyers If an offer is accepted the corresponding record is updated This information is stored in the variables Seller Buyer Creator and Price If a seller makes an offer the variable Seller is set to the Subject variable of this subject Since this number is unique we also say that this is the subject ID The variable Buyer is set to 1 which means that this is an open offer The variable Price is the price the seller enters as her offer When a buyer accepts a seller s offer the number 1 in the variable Buyer is replaced by the subject ID of the buyer The analogous changes to the contracts table are made if a buyer makes an offer and if a seller accepts a buyer s offer As you have seen it is easy to map the creation and acceptance of offers in the contracts table If an offer is accepted it is not sufficient to mark the offer as accepted Think of a seller who makes de creasing offers whose lowest offer is eventually accepted It is clear that the other open offers of this seller are no longer valid For instance it is possible that this seller has no more goods to sell Therefore we have to delete the outdated offers Obviously we do not want to actually delete these offers in the table since we want to have a record of all actions taken by subjects We only want to ma
275. xt ED Choice of the other player OUT OthersChoice ED Please wait until the experiment continues m a ED Your income in this period OUT Profit E continue Waitingscreen Figure 3 10 Stage tree of the battle of the sexes game In this experiment the players may have different roles However they differ only with respect to the parameters They have different payoff functions We implement this in the following way First we define in the Background defaults for the payoff matrix The variable Pi_BC_ is the payoff of a player if he plays as B and the other player plays as C For instance Pi21 is the payoff the player gets if he plays as 2 and the other player plays as 1 The actual parameters for the different subjects are then defined in the parameter table as shown in the following figures Teilnehmer 1 Runde 1 Teilnehmer 2 Runde 1 Gruppe 2 Cancel this player prefers 2 Pill 2 Gruppe Name Programm this player prefers 1 Pill 3 Pil2 1 Pi21 0 Pi22 2 Pil2 0 Pi21 1 Pi22 3 Figure 3 11 Parameter table of the battle of the sexes game To calculate the payoff we need to know the choice of the other player Because the other player s variable Choice is not in one s own record we have to apply a table function The function find runs through the table and returns an entry as soon as some condition is met The other player s record has the properties that th
276. ynorsk Polish Portugues Russian Command Line Option ar arab arabic id indonesian br brasil cat catala catalan cn chinese cz cesky czech dk dansk danish nl nederlands dutch en english fi suomi finnish fr francais french de deutsch german gr greek il ivrit hebrew it italiano italian jp nihongo japanese hu magyar hungarian ms melayu malay mng mongolian no norsk norwegian nyno nynorsk newnorwegian pl polski polish pt portuguese portugues ru ruskii russian Codepage 1256 1252 1252 1252 936 Simplified GBK 1250 1252 1252 1252 1252 1252 1252 1253 1255 1252 932 Shift JIS 1250 1252 1251 1252 1252 1250 1252 1251 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Command Line Options z Tree 3 5 Command line options for z Tree Reference Manual Language Command Line Option Codepage Slovenian sv Slovensky slovak 1250 Spanish es espanol spanish 1252 Swedish se svensks swedish 1252 Swiss German Zurich style zh zuerituetsch zurichgerman 1252 Turkish tr turkce turkish 1254 Ukraine ua ukrainska ukraine 1251 Vietnamese vi vietnamese 1258 channel ch Determines the channel through which the z Leaves establish contact to z Tree If you want to run more than one z Tree on one computer they must work with different channels i e
277. you set the channel to values greater than one Defaults to 0 11 2 Command line options for z Tree xlsdir dir Sets the directory where the xls file is stored sbjdir textsldir Sets the directory where the subjects file is stored zttdir dir Sets the directory where the treatment and questionnaire files are automatically stored before they run datadir dir Sets the directory where the xls and the subjects file sbj are stored as well as treatment and ques tionnaire files adrdir dir Sets the directory where the address file is stored paydir dir Sets the directory where the payment file is stored privdir dir Sets the directory where the address and the payment file are stored gsfdir dir Sets the directory where the GameSafe is stored tempdir dir Sets the directory where the temporary files lastclt txt db txt and prevdb txt are stored leafdir dir Sets the directory where the file server eec is stored treatment file Opens the treatment specified in fi 1eand starts it as soon as sufficiently many clients are connected checkdiskspace size Checks whether there is sufficient disk space on the hard drive Page 172 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Command Line Options z Tree 3 5 Command line options for z Leaf Reference Manual asksessionname When z Tree starts a prompt appears in which a name for the session can be entered
278. ys when a subject enters stage When last subject enters stage Used Variables comma separated Figure 8 2 Table dialog Name Name of the table Lifetime How long the table can be used Period The table is reconstructed after each period As in the subjects or globals table you get access to the data of the previous table with the prefix OLD in front of the table name Treatment The table is available during the treatment At the end of the treatment it is destroyed after being stored of course Page 112 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Menu Commands z Tree 3 5 Treatment Menu Reference Manual Session As is the case for the session table the table survives the end of the treatment Program execution You can specify whether programs defined for the table at the beginning of a stage are executed when the first subject enters the stage when the last enters or always when a subject enters that stage Used Variables For a table with lifetime session you can define what variable are used This allows them to be used in a program without having to define them within the treatment 8 3 4 New Table Loader A table loader reads in a file that contains tables The format corresponds to the z Tree output file format It is tab separated In the first column there is the name of the table Each table starts with a header line
279. ze of label This is the maximum width of the label When the display is given in a percentage this refers to the width between the left and right margin and not to the width of the whole screen 8 4 5 New Question Questions in questionnaires correspond to items in treatments In items display options are defined in the field layout Here they can be set with radio buttons The fields are as follows Label Name of the question as it is shown to the subjects If no variable is set the label appears as text over the whole width of the screen Variable If it is an input variable this is the name of the question as it should appear in the data file If input is not set it has to be a variable of the session table Type Layout of the question Page 145 University of Zurich Department of Economics Thurgau Institute of Economics at the University of Konstanz 20 2 2015 Menu Commands z Tree 3 5 Questionnaire Menu Reference Manual Text Number A text field appears into which input is entered In the case of the number option there is a check to see if it is really a number that has been entered Furthermore the check determines whether the number is in the valid range If the option Wide is selected for a text field the entry field may consist of several lines The number of lines can be selected Buttons A button is created for every line in the field Options Of course only one question with this option is permitted per question form

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