50 minutes. Self-marked. 12 marks. Write your answers, open the model answer, then tick each mark you earned honestly. Nothing is sent or stored.
Scenario (invented)
A gym’s advert reads: “Exercise is proven to cure depression: a huge review found an effect of 0.43!” The advert cites an overview with a median effect of −0.43 for depression against usual care. The overview rated 77 of its 97 reviews “critically low” in quality.
Task 1 (2 marks)
Use the table in M6.L1 to give the chance of superiority for d = 0.43, and say what it means.
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Task 2 (3 marks)
Rewrite the advert’s headline claim so it is accurate.
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Task 3 (3 marks)
List three problems with the advert.
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Task 4 (4 marks)
Write the five-line evidence card for “physical activity improves mood” and choose a safe habit for your own experiment, with one reason.
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Rubric and model answer
Task 1 (2 marks)
About 62%. If you pick one treated person and one comparison person at random, the treated person has the better outcome about 62 times in 100, against 50 for no effect.
Task 2 (3 marks)
For example: “Across many trials, physical-activity programmes were linked to moderately lower depressive symptoms than usual care, though the quality of the underlying reviews was often low.”
Task 3 (3 marks)
Any three: “proven” and “cure” are too strong; 0.43 is a median, not a result for everyone; 77 of 97 reviews were critically low in quality; usual care is not a placebo and trials are not blinded; the evidence mostly concerned mild-to-moderate depression; “huge” overstates a moderate effect; the advert sells a product.
Task 4 (4 marks)
Claim: physical activity improves mood. Mechanism: proposed, such as activity, routine and social contact. Best evidence: overview of 97 reviews, 1,039 trials, median d about 0.43 for depression. Strength: Moderate. Limits: review quality, usual-care comparison, no blinding, mild-to-moderate cases. Habit: a short daily walk at a fixed time, because it is gentle, easy to log and low risk.
Marks so far: 0 of 12