A researcher compares 80 people who join Alcoholics Anonymous (AA) with 80 people who decide not to join. On the average, those in the AA group and those in the non-AA group have equal alcohol problems at the start. One year later, on the average, those in the AA group are healthier and are drinking less than those in the non-AA group. What is wrong with this study that prevents us from evaluating the effectiveness of the AA procedure?

Question

Quizplus · Accepted Answer

There is a lack of random assignment to groups, meaning that participants were not randomly assigned to either the AA group or the non-AA group. This introduces the possibility that there are pre-existing differences between the two groups that could affect the outcome, making it difficult to attribute any differences observed to the AA procedure itself. Therefore, we cannot conclude that the AA procedure is the reason for the observed differences in alcohol consumption and health outcomes between the two groups.

A Researcher Compares 80 People Who Join Alcoholics Anonymous (AA)