What is the purpose of randomisation in a trial?
To test whether a new drug works, researchers compare it with a control. In a randomised trial, patients are assigned by chance to the drug group or to a group that receives a placebo, a pill with no active ingredient. Randomisation makes it likely that the groups are alike in age, severity of illness and other factors, so that any difference in outcome can be traced to the drug. In a blinded trial, patients do not know which pill they have received, and in a double-blind trial neither do the doctors who assess them, because expectations can colour what people report and see. Even so, a trial has limits. Patients who volunteer may differ from the wider population, and a trial that lasts a few months cannot show long-term harm. Large trials reduce the effect of chance, but they cost more and take longer. A small trial may fail to detect a real benefit.
Answer and explanation
Correct answer: C. To make the groups alike so that differences can be traced to the treatment
- Step 1: The text says randomisation makes the groups alike. Step 2. Then a difference in outcome can be traced to the drug. Answer: to make the groups alike. Why not the others: these are not purposes of randomisation.
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