One hundred volunteers who have agoraphobia are available for a study. Fifty are selected at random and are given the drug imipramine, which is believed to be effective in treating agoraphobia. The other 50 are given a placebo. A psychiatrist evaluates the symptoms of all volunteers after two months to determine if there has been substantial improvement in the severity of their symptoms.
Suppose the volunteers were first divided into men and women, and then half of the men were randomly assigned to the new drug and half of the women were assigned to the new drug. The remaining volunteers received the placebo. What would this be an example of?

Question

Quizplus · Accepted Answer

This is an example of block design, where the volunteers are first divided into blocks based on their gender, and then randomly assigned within each block to either the drug or placebo group. This helps to account for any potential gender differences in the response to the treatment.

One Hundred Volunteers Who Have Agoraphobia Are Available for a Study