Using data from Exercise 10.28 on the effects of posthypnotic suggestion on the Stroop effect (Raz, Fan,

& Posner, 2005), let’s conduct an independent-samples t test. For this test, we will pretend that two sets of people participated in the study, whereas previously we considered fictional data collected from the same participants in a within-groups design. The first score for each participant will be in the first sample—those not receiving a posthypnotic suggestion. The second score for each participant will be in the second sample—those receiving a posthypnotic suggestion. So we have used the data from Exercise 10.28 to create two separate groups:

Sample 1: 12.6, 13.8, 11.6, 12.2, 12.1, 13.0 Sample 2: 8.5, 9.6, 10.0, 9.2, 8.9, 10.8

a. Conduct all six steps of an independent-samples t test. Be sure to label all six steps.

b. Report the statistics as you would in a journal article.

c. What happens to the test statistic when you switch from having all participants in both samples to having two separate samples? Given the same numbers, is it easier to reject the null hypothesis with a within-groups design or a between-groups design?

d. In your own words, why do you think it is easier to reject the null hypothesis in one of these situations than in the other?