Problem-Solving and Data AnalysisMediumWhat random assignment licenses
Problem-Solving and Data Analysis practice question
Two hundred forty volunteers agreed to take part in a study of study techniques. Each volunteer was randomly assigned to use either technique A or technique B for six weeks, after which all of them took the same test. The group using technique A scored significantly higher on average.
Which conclusion is best supported?
- A. For the volunteers in this study, technique A caused the higher average test score.Correct
- B. For all students nationally, technique A causes higher test scores.
- C. There is an association between technique and score, but no causal conclusion is possible from this design.
- D. Technique A and technique B are equally effective.
Answer: A. For the volunteers in this study, technique A caused the higher average test score.
Volunteers were randomly ASSIGNED to the two techniques, which makes the groups comparable at the start, so a significant difference at the end is reasonably attributed to the technique. Because the volunteers were not randomly selected from a wider population, that causal conclusion applies to this group rather than to students generally.
Why the other answers are wrong
- B. For all students nationally, technique A causes higher test scores.
- Random assignment supports a cause; it does not support generalising beyond the people studied. These were volunteers, not a random sample of students nationally, so the result may not carry over.
- C. There is an association between technique and score, but no causal conclusion is possible from this design.
- This is the right caution applied to the wrong design. Random assignment is exactly what licenses a causal conclusion — it's the absence of assignment, as in an observational study, that limits you to association.
- D. Technique A and technique B are equally effective.
- The study found a significant difference between the groups, so concluding they are equally effective contradicts the result.
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