Most studies would not work if subjects were aware in detail about the study question. People would (unconsciously) modify their behavior. You gave consent and were aware that it is a study. It is ethically okay for the researcher to work with reasonable distractors to assure research validity.
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According to the Belmont Report principles. This certainly does not minimize the risk for the absolutely necessary.
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That depends on the study. If subjects are informed about this possibility, if they understand it, and voluntarily agree to participate, this can well be. Please review the lecture:
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That would be your task as a researcher, if that makes a difference to you.
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