9.38 The following are mood scores for 12 participants before and after watching a funny video clip (lower values indicate better mood).

Before After Before After 7 2 4 2 5 4 7 3 5 3 4 1 7 5 4 1 6 5 5 3 7 4 4 3

a. Calculate the paired-samples t statistic for these mood scores.

b. Using a one-tailed hypothesis test that the video clip improves mood, and an alpha level of 0.05, identify the critical t values and make a decision regarding the null hypothesis.

c. Using a two-tailed hypothesis test with an alpha level of 0.05, identify the critical t values and make a decision regarding the null hypothesis.

9.39 Consider the following data: Score 1 Score 2 Score 1 Score 2 45 62 15 26 34 56 51 56 22 40 28 33 45 48

a. Calculate the paired-samples t statistic.

b. Calculate the 95% confidence interval.

c. Calculate the effect size for the mean difference.