During an experiment on police officer fitness, several members of the control group become self-conscious about their weight and begin vigorously exercising. This external threat to validity is called:

Question

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Reactivity refers to how participants in a study may change their behavior simply because they know they are being observed or tested. In this case, the control group members became self-conscious about their weight and began exercising because they knew they were being monitored for police officer fitness. This is an example of reactivity as an external threat to validity.

During an Experiment on Police Officer Fitness, Several Members of the Control