Be A Juror Experiment

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Introduction
Method
Data Analysis
References


Introduction
Eyewitness testimony research is fun to participate in, fun to read about, and has important practical applications (Wells, Malpass, Lindsay, Fisher, Turtle, & Fulero, 2000 ). The present study, originally proposed by Thompson (1992), is very useful for instructional purposes. At a basic level, it can be used to talk about people's susceptibility to eyewitness testimony. At a more advanced level, it can be used to show the value of using multiple group designs and as a jumping off point for explaining how to do post-hoc tests.

Method

Participants in this study are asked to rate their attitude about a defendant's guilt on a 1 (definitely not guilty) to 7 (definitely guilty) scale. There are three conditions (1) a no eyewitness condition, (2) a discredited eyewitness, and (3) an unrefuted eyewitness.  The conditions variable is a between subjects variable.


Data Analysis and Anticipated Results

Usually, the main effect for eyewitness condition (no eyewitness vs. discredited eyewitness vs. unrefuted eyewitness) will be statistically significant. Often, post hoc tests will find that (1) participants in both eyewitness conditions see the defendant as more guilty than participants in the no-eyewitness condition and (2) the eyewitness conditions will not differ from each other.

Data Format in Downloadable csv file
The data obtained via the Download data link on the PsychExperiments homepage are comma delimited.  The first entry (up to the first comma) is the affiliation of the research participant.  Typically this is the class to which the participant belongs.  Non-affiliated participants use the default entry of Interested Person. Next is the randomly assigned ID code for the research participant. The third entry is the date. The fourth is a measure of "experiment time" in seconds.  This is how long it took the participant to complete the experiment, beginning with Trial 1 and ending with the last trial.  (Time spent reading instructions etc. are not included).  The measure is useful as a screen for "bad" data.  The time measure should be appropriate to the task--not too fast and not too slow.  Next come entries for the gender of the participant ("M" or :F") and age of the participant.  Next are the raw data for the experiment. The raw data presentation begins with the number "1," which stands for Trial 1 in this one-trial experiment. (Other experiments frequently have multiple trials.)  Next is the number 1, 2, or 3 to indicate the condition to which the participant was assigned (1= No eye witness, 2 = discredited eye witness, 3= unrefuted eye witness.) Last is the number 1-7 used to assign guilt.  The table below shows the format trial data in tabular form.  Not included in the tabular display are the user information (affiliation, ID, data, and time) which precede these data, as shown in the text line below the table. 

Trial Number Condition Guilt
1, 2, 4,

Florida State University--Aveyards EXP 3503L,ZWV595,11/10/2004,71,F,27,1,1,4,
 

References

          Thompson, B. (1992, August). Making data analysis realistic: Incorporating data collection into statistics courses. Paper presented at the meeting of the American Psychological Association, Washington, D.C.

          Wells, G. L., Malpass, R. S., Lindsay, R. C. L., Fisher, R. P., Turtle, J. W., & Fulero, S. M. (2000). From the lab to the police station: A successful application of eyewitness research. American Psychologist, 55, 581-598.
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Last revised:November 16, 2004 11:30:56 AM
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