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Question:

Twenty people suffering from a disorder recover when given a particular drug. In order to verify that it was that drug that was responsible for their recovery, a hundred other people with this disorder are recruited into a clinical trial. Fifty subjects are given the drug, and fifty are given a placebo. Which of the following procedures would be most effective in testing whether the drug is responsible for their recovery?

A Ensure that neither the subjects nor the investigators know which subjects are given the drug and which are given the placebo.
Explaination

In clinical trials and similar investigations, the most effective experiments are “double blind”, with neither the investigator nor the subject knowing who is in the treatment group and who is in control group. This is important in order to eliminate bias. If the subjects know they are being given a placebo, they may be more likely to not report any changes, or they may over report positive effects. If investigators know which subjects are given the placebo, they may inadvertently attach importance to subjects who are receiving the drug. Even if both the subjects and the investigators strive to be objective and not be swayed by their knowledge, the results may be biased unconsciously. Ensuring that neither the subjects nor the investigators know which subjects are the controls until the test is over prevents this bias from occurring.