a = 0.05. A therapist would like to evaluate the effectiveness of a procedure for treating depression. A sample of n = 16 depressed clients is obtained, and each person's level of depression is measured using a standardized questionnaire before they begin the therapy program. Two weeks after therapy, each client's level of depression is measured again. The average level of depression dropped by 6.8 points following therapy. The difference scores had a variance of 64.
a. State the null hypothesis.
b. Which statistical test would you use to test this hypothesis?
c. Calculate the appropriate test statistic and state your conclusions. Show your work.
d. Compute an effect size.
e. Find the critical value.