## Participate in a multiple group experiment

Students can participate in this online, three-group, eyewitness testimony experiment.
A data file containing each participant's condition number (1= eyewitness is 50% confident, 2=eyewitness is 75% confident, 3= eyewitness is 100% confident) and rating of the defendant's guilt (1= sure the defendant is not guilty; 7 = sure that the defendant is guilty) is available from this link.

Data from each participant is separated by the word "endline." Thus, suppose we had data from 3 participants: (a) a person in the 50% confidence group who rated the defendant's guilt as a "3," (b) a person in the 75% confidence group who rated the defendant's guilt as a "4," and (c) a person in the 100% confidence group who rated the defendant's guilt as a "7." In that case, the data file from the above link would look like this:
1, 3 endline
2, 4 endline
3, 7 endline

If you want to create a data file that contains only your students' data, tell your students to put a certain number (e.g., 8) in the code number box. That number will put your class's data in a separate file. For example, if they all put the number 8 in the box,
their data will be stored in the file http://markwebtest.netfirms.com/data/c11eyewitnessA8.txt
If, on the other hand, they all put the number 66 in the box, their data will be stored in the file
http://markwebtest.netfirms.com/data/c11eyewitnessA66.txt

If you give your class a code number, the data file will contain more than just the condition number and the score on the rating scale. For example, for the three participants mentioned above, the data file might look like this:
0/17/105, 9:19:16, 60.15.41.14, http://markwebtest.netfirms.com/cgi-bin/randassign3m.pl, 1, 3 endline
0/17/105, 9:20:30, 60.15.41.14, http://markwebtest.netfirms.com/cgi-bin/randassign3m.pl, 2, 4 endline
0/17/105, 9:21:12, 60.15.41.14, http://markwebtest.netfirms.com/cgi-bin/randassign3m.pl, 3, 7 endline

Such a data file would tell us that all three scores came from individual(s) who participated in the experiment on the same day (0/17/105 means January 17, 2005), at about the same time (between 9:19 and 9:21), using the same computer (a computer with the IP address of 60.15.41.14), and using the same website
( http://markwebtest.netfirms.com/cgi-bin/randassign3m.pl).

Alternatively, you could have the class conduct their own multiple-group experiment. For example, they could modify this online experiment or, as Burt Thompson suggested, they could base a three-group experiment on the study described on pages 9-10 of

Loftus, E. F. (1979). Eyewitness testimony. Cambridge, MA: Harvard University Press.

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