An experimenter tests the hypothesis that physical exercise improves people's mood.Subjects in the experimental group participate on Monday and Tuesday and those in the control group on Wednesday and Thursday.What is the extraneous (confounding)variable?

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The day of the week is a confounding variable because it is not controlled in the study and could impact the results. For example, it is possible that people in the experimental group were happier on Monday and Tuesday than the control group simply because those days of the week are typically less stressful or more enjoyable. To eliminate this confounding variable, the experimenter should have randomly assigned subjects to participate on different days of the week.

An Experimenter Tests the Hypothesis That Physical Exercise Improves People's