Final answer:
The control group in the study where 80 students are recruited to assess the impact of a review session on exam performance comprises the students studying as normal, since they are not receiving the experimental treatment, which is the review session.
Step-by-step explanation:
In the scenario where a researcher recruits 80 students for a study to examine the effects of a review session on exam performance, the control group would be the students studying as normal. This is the group that does not receive the experimental manipulation, which in this instance is the review session. The remaining students who attend the review session would form the experimental group, as they are exposed to the independent variable (the review session). It is crucial to have this control group as a baseline to compare against the outcomes of the experimental group.
Experimental design often requires random assignment to ensure that each participant has an equal chance of being placed in either group, which helps to avoid selection bias. Additionally, measures such as blinding can be taken to prevent experimenter bias, ensuring that results are not influenced by the researchers' expectations.