In a Study on Effectiveness of Therapy in Treating Depression

Multiple Choice

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