In a trial, what is the purpose of including a placebo group?

• A. To determine whether improvements are due to the treatment or to the placebo effect
• B. To provide active treatment to all participants
• C. To speed up the trial
• D. To reduce costs

Answer: (A)

The main goal is to separate true effects of the treatment from placebo or non-specific effects. A placebo group receives an inert substitute, so any improvement there can be attributed to placebo effects, natural disease changes, or study participation. If the treatment group improves more than the placebo group, we can attribute the additional benefit to the active therapy. The other choices miss this purpose: giving active treatment to everyone undermines the comparison, and claims about speeding up trials or reducing costs aren’t the primary reason for including a placebo group.