A third major advantage of a clinical trial is that conditions are controlled as carefully as possible, minimizing potential biases. Both sampling and measurement bias are greatly reduced, if not eliminated. In contrast, survey studies are generally subject to significant sampling and measurement bias.

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(1) A statement that the study involves research, an explanation of the purposes of the research and the expected duration of the subject’s participation, a description of the procedures to be followed, and identification of any procedures which are experimental;

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