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1. What is WEXTOR?
WEXTOR is a Web-based tool for generating and visualizing experimental designs and procedures. It can be used to design laboratory and Web experiments in a guided step-by-step process. WEXTOR supports complete and incomplete factorial designs with between-subjects, within-subjects, and quasi-experimental factors.

2. For whom is WEXTOR intended?
WEXTOR is useful to
• students who are familiar with basic internet techniques and want to learn about experimenting
• experienced experimenters who know about experimental design and want to learn about specifics of Web-based experimenting
• experienced Web experimenters who need a fast tool to create experimental designs and procedures

3. Is WEXTOR legal for educational and non-commercial uses?
Yes, you may use WEXTOR freely for educational and non-commercial uses. If you want to use WEXTOR for commercial use, please contact us!

4. I'm new to online experimenting. Where do I start?
For more about WEXTOR, read WEXTOR at a glance. Also, read Standards for Internet-based experimenting (pdf, 124KB).
There's also a Tutorial (pdf, 6.9MB) featuring screenshots and detailed descriptions, and a guideline with helpful hints (pdf, 84KB).

5. Where can I get a WEXTOR trial account?
See the registration page for more details.

6. How do I change my password?
To change your password, go to the My Account page.

7. Why should I get a paid account?
There are four reasons: • Downloading of data in 'each-participant-a-line-each-variable-a-column' format from an experiment hosted by us (more work!) is available in paid account mode only.
• Trial accounts will stop working after 6 months — by paying you can reactivate your experiments.
• The data file contains a variable that lets you see a participants path through your experiment (e.g. use of the back button).
• You support our work. A license is €40 for a single account. Other licenses are available. Please contact for details.

8. How and where can I conduct my Web experiment?
In order to carry out your Web experiment, you need to generate, download, edit and then upload your materials to the WEXTOR server. Alternatively, you may instead run your Web experiment on your own Web server. Participants for Web experiments can be recruited in online laboratories, such as the web experiment list or the Web Experimental Psychology Lab.

9. How does WEXTOR collect data?
Data will be recorded to the log file of the Web server. Generally the log file is used to log client requests made to the Web server. Each log file entry consists of a sequence of fields, containing information on the time at which transactions are completed, the requested file, the participants answers etc. If you use WEXTOR to upload and host your experiment, the resulting log file will be freely available to you for download. We recommend to use Scientific LogAnalyzer for the analysis of log files beyond sample sizes of about 60 persons and designs of more than 10 Web pages each person has to go through. Smaller log files can easily be analyzed by hand. Comfort option: Download of data is also available in Excel/SPSS ready 'each-participant-a-line-each-variable-a-column' format. This option is available separately in paid account mode. Please contact for details.

10. Which information should the log file contain?
Most Web servers provide very flexible logging capabilities. The log file is usually written in a customizable format. In order to analyze your log file using LogAnalyzer, your log file should contain the following information: connection ID, date and time at which transaction completed, result, IP address of the client which made the request to the Web server, URL path requested, bytes sent, user agent, referer, time taken to serve the request, and search arguments. If you use WebSTAR the log file might appear like this:


If you use the Apache HTTP Server, the configuration for the log file might look as follows:

LogFormat "%P\t%{%m/%d/%y}t\t%{%T}t\t%c\t%h\t%U\t%B\t%{User-Agent}i\t%{Referer}i\t%T\t%q\t%D" wextor
CustomLog "/var/log/httpd/access_log_wextor" wextor

For more information about this topic, read our tutorial Apache HTTP Server - Configuring the logging capabilities or check out Apache's Log Files docs.

11. Which method is used to send data to the Web server?
WEXTOR simulates a GET method form submission that looks anything like this:

Basically the above URL is simulating a HTML form submission that looks something like this:

<FORM METHOD="GET" ACTION="file2.html">
<INPUT TYPE="radio" VALUE="female" NAME="sex">
<INPUT TYPE="radio" VALUE="male" NAME="sex">
<INPUT TYPE="text" NAME="age">
<INPUT TYPE="submit" VALUE="Submit">

Although they look completely different, both of these examples will have the same result: a variable named sex with the value female and a variable named age with a value of 29 is passed to the Web server.

Generally the GET method transmits data by appending it to the end of the desired URL. There can be an unlimited number of variable/value pairs following the question mark, each separated by an ampersand "&". There is a restriction on the GET method: it has a limit of approximately 1024 characters. This means that any submission that may exceeds 1024 characters must be done through the POST method.

12. I would like to conduct part of my Web experiment with participants sitting in class/a lab at my school. However, for some reason access is not possible/blocked. What can I do?
Some institutions limit access to the Internet. You may try the following, then contact your local IT department to make the necessary changes to your local configuration.
  1. A connection problem may occur, if the institution is using a proxy server that uses the same port as WEXTOR (8080). In this case, change "8080" to "8081" in your experiment's URL.
  2. Participants from within your institution may experience certain issues with some pages in your Web experiment, e.g. submit buttons not working, error messages saying all fields need to be filled in, even though all fields are filled in. These problems happen, if the institution as a whole or the participant computer blocks sending of the following information: the current page's address (the so-called "REFERER"), the information appended to the URL (session ID, form entries etc.).
  3. Participants from within your institution all receive an error message saying that Javascript is not working and thus they cannot participate. Have your IT department enable Javascript in the computers' Web browsers and have them make sure that the institution is not blocking files ending in .js
13. Is there a way to have some conditions appear more frequently than others (i.e., not totally random assignment to condition), such that - for example - one of the conditions appears 2-3 times more often than the others?
Yes, you can simply edit the "array" in the start.html Javascript to reflect the desired frequency. E.g., have a condition appear twice in the array, if you would like to see it being assigned twice as often as the other conditions.