In a study on effectiveness of therapy in treating depression, participants are randomly assigned to groups so that 10 receive cognitive behaviour therapy (CBT)and 10 are assigned to a no-treatment control condition. The outcome improvement scores for participants in the CBT group are quite different from each other (e.g., some had minimal improvement scores, while others showed large benefits). This discrepancy is referred to as:
A)The third variable problem
B)The directionality problem
C)Within-group variance
D)Between-group variance

Question

Quizplus · Accepted Answer

Within-group variance refers to the variability or differences within a group, which in this case is the CBT group. The fact that there is a range of outcome improvement scores within the CBT group suggests that there is within-group variance. The other answer choices do not accurately describe this situation. The third variable problem refers to the possibility of a confounding variable affecting the relationship between the independent and dependent variables. The directionality problem refers to the uncertainty of the direction of the relationship between variables. Between-group variance refers to the differences between groups.

In a Study on Effectiveness of Therapy in Treating Depression