Why is a random assignment planned? (Passage: Exam stress)
A survey of 2,000 sixth-form students found that 62 per cent reported feeling very anxious before exams. Of these, those who practised short breathing exercises reported lower anxiety afterwards than those who did not. The researchers cautioned that the students chose for themselves whether to do the exercises, and those who did so might have been less anxious or more motivated from the start. A follow-up study is planned in which students are assigned to the exercises or to a waiting list at random.
Answer and explanation
Correct answer: D. To avoid students' own choices explaining the difference
- Step 1: Self-selection problem. Step 2. Random assignment removes the effect of who chooses the exercises. Answer: To avoid students' own choices explaining the difference. Why not the others: The others are not purposes of randomisation.
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