A researcher is interested in comparing effectiveness of three different kinds of therapy for anger problems. 8 participants are randomly assigned to three treatment conditions: Cognitive Therapy (CT), Cognitive-Behavioral Therapy (CBT), and Interpersonal Therapy (IT). All participants complete weekly treatment for 8 weeks. Participants take an anger test before and after the 8-week treatments. Each participant's difference score (= anger score after the treatment minus (-) anger score before the treatment) is shown in following table. The three therapists in this experiment have equal educational levels as well as clinical experiences.
CT CBT IT
3 5 7
4 4 8
4 6 9
4 6 10
3 5 6
8 4 7
6 9 11
2 7 10
a. What statistical test should be employed to examine the data?
b. Determine H0 and Ha for this study.
c. Conduct the appropriate analysis.
d. Should H0 be rejected? What should the researcher conclude?