Controlled trial

A method of testing the effectiveness of new treatments or comparing different treatments. In a typical controlled drug trial, 2 comparable groups of patients suffering from the same illness are given courses of apparently identical treatment. However, only one group receives the new treatment; the second control group is given a placebo. Alternatively, the control group may be given an established drug that is already known to be effective. After a predetermined period, the 2 groups are assessed medically. Controlled trials must be conducted “blind’’ (the patients do not know which treatment they are receiving). In a “double-blind’’ trial, neither the patients nor the doctors who assess them know who is receiving which treatment.


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