A study is conducted to determine the effectiveness of group therapy on abstinence among older people who are substance abusers. The older people involved in the study either receive group therapy or they are in a comparison group. The presence of a comparison group suggests
A) older people were randomly assigned to one of the two groups (group therapy or comparison)
B) older people were not randomly assigned to one of the two groups (group therapy or comparison)
C) the two groups are equivalent on all important characteristics
D) all alternative explanations can be ruled
E) the two groups were matched on important characteristics

Question

Quizplus · Accepted Answer

The presence of a comparison group alone does not imply random assignment or that the groups are equivalent or matched on all important characteristics; it simply means there is a group against which the treatment group's outcomes can be compared. Random assignment (A) and equivalence/matching of groups (C, E) require specific methodologies that are not implied by the mere presence of a comparison group. Similarly, ruling out all alternative explanations (D) requires more than just having a comparison group.

A Study Is Conducted to Determine the Effectiveness of Group