What is the purpose for using a control group in an experiment? A. It is necessary to ensure the external validity of the study B. It provides a baseline to evaluate the size of the treatment effect...

What is the purpose for using a control group in an experiment? A. It is necessary to ensure the external validity of the study B. It provides a baseline to evaluate the size of the treatment effect C. It minimizes the threat of a confounding variable D. It is necessary to ensure the internal validity of the study