A placebo is an important element of many clinical trials be

A placebo is an important element of many clinical trials because

A: use of the placebo can help avoid confounding.

B: it serves as a control for the experiment.

C: it allows the researcher to adjust for psychological effects of receiving medical attention

.D: All of the above.

Solution

All the reasons provided in options A, B and C are correct. So the correct option to choose is option D (All of the above).