What methods do researchers use to make sure their studies are not biased? Select all that apply.

Randomly assigning participants helps prevent preexisting differences between groups from affecting the results. A group that does not receive the treatment provides a comparison, and keeping researchers unaware of group assignments can reduce bias in how they conduct or interpret the study. Participants knowing their group is not a way to reduce bias, and findings should be checked by others rather than printed before review.

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