Question

One hundred volunteers who have agoraphobia (fear of open and crowded space) 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.

What type of study is this?
A. Matched pair design
B. Observational study
C. Completely randomized block design
D. Completely randomized design

Answer 1

D. Completely randomized design

Explanation:

Based on the description given about the experiment above and the manner in which the subjects were assigned to each of the treatment groups available, we can deduce that the study was conducted using a completely randomized design. The subjects weren't matched or blocked for any variable such as sex, height, age or any other variable. They were just evenly split randomly into the two available treatment levels ( those who receive the treatment and the placebo) group. With this design, all subjects have an equal chance of being in any of the two groups and the selection bias is almost totally eliminated using this sort of design as errors are being considered as arising from experimental faults.