A researcher is interested in examining whether knowledge of a previous criminal record will affect the jury�fs decision to acquit or convict the defendant. The researcher shows 15 participants a 4-hour trial in which a woman is accused of passing bad checks. Participants were divided into three groups based on what they were told about the defendant�fs criminal past: criminal record group (defendant had a criminal past), clean record (no criminal past), or no information group (no information regarding criminal past). Participant�fs then rated the defendant from 1 (completely innocent) to 10 (completely guilty). The data are presented below. Perform the appropriate statistical test (using statistical hypothesis testing) and any necessary post hoc tests to determine whether prior criminal history affects juries.
n=5 ‡”X2 = 589 T1= 40 T2= 20 T3=5
Here are a few hints:
Check out a one-way ANOVA for this kind of problem. Do the calculations to find the F-ratio to compare to the critical or cutoff value from the F-distribution table (used for ANOVA tests). Find the critical or cutoff value at .05 level of significance using the table to reject the null hypothesis (which would state that all population means are equal). If the null is rejected in favor of the alternate hypothesis (which would state that all population means are not equal), then you can conclude a difference.
One of the most common post hoc tests include Tukey's HSD test. There may be others you can use as well.