Gouzoulis-Mayfrank et al. (2000) examined task performance of users of the drug Ecstasy and compared that with a group of Cannibis users and a control group of Nonusers. There were 28 participants in each group, and the Ecstasy users were almost all users of Cannibis as well. Performance was evaluated on several different tasks, but we will focus on a test of abstract thinking. The data given below were created to have the same means and variances as in the original study, and higher scores represent better performance. The data are available on the Web site as Ex11-33.dat.
a. Run an analysis of variance comparing the means of the three groups.
b. Calculate Cohen’s d to examine the pairwise effect sizes—in other words, calculate d on the comparison of each group with each of the other groups.
c. What is a reasonable set of conclusions from this study?
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