A researcher designed an experiment to determine if consumption of caffeine results in increased level of motor activity. The study was done at 7 AM each day. A confounding variable could be

Question

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The time of day could be a confounding variable because it might independently affect the level of motor activity, making it difficult to determine if changes are due to caffeine or the time of day.

A Researcher Designed an Experiment to Determine If Consumption of Caffeine