ACT (Enhanced)ScienceMedium
A medical researcher is conducting a study to determine the efficacy of a new vaccine against a common viral infection. They recruit 1,000 participants and randomly divide them into two groups. Group A receives the new vaccine, and Group B receives a placebo. Neither the participants nor the researchers administering the treatments know who is receiving the vaccine or the placebo. After six months, the number of infection cases in each group is recorded. What is the primary purpose of using a placebo in this experimental design?
- ATo ensure that all participants receive some form of treatment.
- BTo provide a baseline for the natural incidence of the infection in the population.
- CTo isolate the effect of the vaccine by controlling for the placebo effect.
- DTo blind the participants to which treatment they are receiving.
Show answer & explanationAnswer & explanation
Correct answer: C. To isolate the effect of the vaccine by controlling for the placebo effect.
The placebo effect is a psychological or physiological response to a 'treatment' that isn't medically active. By giving a placebo to a control group, researchers can differentiate the true physiological effects of the active treatment from the effects caused by the expectation of treatment.
Why the other options are wrong
- A. While technically true that all receive 'something', the primary purpose is not just to provide a treatment.
- B. While a control group can give insight into natural incidence, the specific role of the placebo is to control for the placebo effect itself, a psychological phenomenon.
- D. Blinding is a separate but related aspect of the experimental design (double-blind), not the primary purpose of the placebo substance itself.
Placebo Effect
A phenomenon in which a patient's physical or mental health appears to improve after taking a placebo or 'sham' treatment. This improvement is not attributable to the placebo itself, but to the patient's belief in the treatment.
- Psychological or physiological response to an inert substance.
- Important to control for in clinical trials.
- Highlights the power of expectation and belief in treatment.
Memory trick: Controls Guard Against False Findings