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Control (or comparison) groups are used in between-subjects research designs, which involve administering different conditions to different groups of people. In some such designs, one level is called the experimental (or treatment) group and one is called the control group. A control group serves as a baseline for comparing the outcome of a condition of interest. Assignment to groups is random, such that every participant has an equal chance of being in any group. Without an appropriate control group, researchers cannot make a valid conclusion about the results of a treatment or intervention.

Designing an Experiment With a Control Group

Participants should be representative of the population, such that when they are randomly assigned to the experimental group or the control group, researchers have confidence that the ...

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