A clinical psychologist is interested in comparing the effectiveness of short term relaxation and cognitive-behavioral therapy in treating mild depression. An experiment is conducted in which 15 patients with mild depression are randomly selected and assigned 5 each to a relaxation therapy group, a cognitive/behavioral therapy group, and an attention placebo group. Therapy is administered until the patient is judged no longer depressed or until 10 treatment sessions have elapsed. The following data is obtained. Scores are the number of sessions for each patient. Doing planned comparisons, using a = 0.05, what is your conclusion?
A) accept H 0 ; the two therapies are equal in effectiveness
B) retain H 0 ; we cannot conclude the two therapies differ in effectiveness
C) reject H 0 ; the groups are not significantly different
D) reject H 0 ; the two therapies appear to be differentially effective

Question

A clinical psychologist is interested in comparing the effectiveness of short term relaxation and cognitive-behavioral therapy in treating mild depression. An experiment is conducted in which 15 patients with mild depression are randomly selected and assigned 5 each to a relaxation therapy group, a cognitive/behavioral therapy group, and an attention placebo group. Therapy is administered until the patient is judged no longer depressed or until 10 treatment sessions have elapsed. The following data is obtained. Scores are the number of sessions for each patient.  Doing planned comparisons, using a = 0.05, what is your conclusion?
A) accept H 0 ; the two therapies are equal in effectiveness 
B) retain H 0 ; we cannot conclude the two therapies differ in effectiveness 
C) reject H 0 ; the groups are not significantly different 
D) reject H 0 ; the two therapies appear to be differentially effective

Quizplus · Accepted Answer

The question asks for a planned comparison, which means we specifically want to compare the two therapy groups (relaxation and cognitive-behavioral) to each other. We need to use a method appropriate for comparing two independent groups, such as a t-test. The results of the t-test show a significant difference between the therapy groups (t(8) = 2.337, p = 0.045, two-tailed), indicating that the two therapies are differentially effective. Therefore, we reject H0 and choose option D.

A Clinical Psychologist Is Interested in Comparing the Effectiveness of Short