In an experiment to study the effects of caffeine on performance, an experimenter asked the male students in an introductory psychology class to drink two regular Pepsis before a test and the female students to drink two caffeine-free Pepsis. She then compared performance of the two groups on the test. A confounding variable in this study is:

Question

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The gender of the participants is a confounding variable because it is intertwined with the independent variable (type of Pepsi) and could independently affect the dependent variable (test performance), making it difficult to isolate the effect of caffeine.

In an Experiment to Study the Effects of Caffeine on Performance