A new cold medicine is being tested. Patients are randomly assigned to receive either the medicine or a placebo. Both look and taste identical, and neither patients nor doctors know which is which.
What is the purpose of including a placebo group in this design?
- A
To allow blocking by symptom severity
- Bcheck_circle
To control for the placebo effect so the medicine's true effect can be isolated
- C
To increase the total number of subjects
- D
To eliminate sampling bias
Explanation
The placebo group experiences any psychological effect of taking a pill, so any extra benefit in the medicine group can be attributed to the active ingredient.