In a trial, 12 of 100 patients on a new drug and 20 of 100 on placebo had a stroke. What is the relative risk of stroke on the drug compared with placebo?
Answer and explanation
Correct answer: B. 0.6
- Step 1: Relative risk is the risk in the treated group divided by the risk in the control group.
- Step 2: 0.12 divided by 0.20 = 0.6, a 40 percent relative risk reduction.
Answer
0.6.
Why not the others: 1.67: this inverts the ratio. 0.08: this is the absolute risk reduction. 0.12: this is the absolute risk with treatment.
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