Problem-Solving and Data AnalysisHardLimits of a randomised trial's result
Problem-Solving and Data Analysis practice question
In a randomised trial, adults who took a supplement slept 20 minutes longer on average than adults given a placebo. A headline says the supplement helps everyone sleep. Which of the following is the best criticism of the headline?
- A. The trial studied adults under particular conditions, so the result cannot be assumed to hold for children or others outside the study.Correct
- B. Randomised trials cannot show cause.
- C. Twenty minutes is too small to measure.
- D. The placebo group should not have existed.
Answer: A. The trial studied adults under particular conditions, so the result cannot be assumed to hold for children or others outside the study.
Random assignment supports cause within the group studied, not for everyone.
Why the other answers are wrong
- B. Randomised trials cannot show cause.
- Random assignment is exactly what supports a causal claim.
- C. Twenty minutes is too small to measure.
- Twenty minutes can be measured.
- D. The placebo group should not have existed.
- The placebo group is what makes the comparison fair.
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