ACT (Enhanced)ScienceEasy
A team of researchers is investigating the effect of a new dietary supplement on muscle growth. They recruit 100 participants and randomly assign them to two groups: one receives the supplement, and the other receives a placebo. Neither the participants nor the researchers administering the supplement know who is receiving the actual supplement. After 12 weeks, muscle mass is measured in both groups. Which of the following best describes the experimental design used?
- ACross-sectional study
- BObservational study
- CDouble-blind study
- DSingle-blind study
Show answer & explanationAnswer & explanation
Correct answer: C. Double-blind study
The experimental design described involves both participants and researchers being unaware of treatment assignments, which is the definition of a double-blind study. This design minimizes bias from expectations.
Why the other options are wrong
- A. A cross-sectional study observes a population at a single point in time, without intervention.
- B. An observational study involves observing subjects without intervention, unlike an experiment with controlled groups.
- D. A single-blind study would only blind one party (either participants or researchers), not both.
Double-Blind Study
An experimental procedure in which neither the participants nor the researchers know which group is receiving the treatment and which is receiving the placebo.
- Minimizes bias from participant expectations (placebo effect).
- Minimizes bias from researcher expectations (observer bias).
- Often used in clinical trials for drug efficacy.
Memory trick: Blinded eyes prevent biased ties.