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# Paired t test comparing the means of two populations

Dr. Justin Case wants to explore whether or not students perform better if they cram for a test (massed practice) or if they space their studying over weeks (distributed practice). The massed practice group studies for 8 hours the night before a quiz; the distributed practice group also studies for 8 hours, but does it in 2-hour blocks the four days before the quiz. The dependent variable is the number of errors made by each pair of subjects. Each pair of subjects is matched for intelligence level. The results are given below. Decide which statistical test would be appropriate for these data, carry out the test, and evaluate the outcome. Assume that the researcher has chosen a p < .01 level of significance and that the direction of the outcome has not been predicted (adapted from Myers & Hansen, 1997, p. 374).

Massed
Distributed

S1: 6
S1: 5

S2: 4
S2: 3

S3: 3
S3: 2

S4: 5
S4: 2

S5: 2
S5: 3

The second number in the set is the distributed.

#### Solution Summary

This solution is a detailed, step-by-step example of how to conduct and interpret a paired t-test for the mean difference between two populations.

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