What is the primary role of a control group in an experiment?

• A. To receive the experimental treatment.
• B. To ensure the experiment uses more variables.
• C. To measure the maximum effect possible.
• D. To establish a baseline by lacking the experimental treatment.

Answer: (D)

The main concept is that a control group provides a baseline for comparison. It does not receive the experimental treatment, and everything else is kept the same. By comparing the outcomes between the control group and the group that does receive the treatment, you can attribute any observed difference to the treatment itself rather than to random variation or other factors. Randomly assigning subjects and keeping conditions consistent helps control for other variables that could affect the result, making the test of the hypothesis more reliable.

Choosing to give the control group the treatment would erase the baseline needed to see the treatment’s true effect. Trying to ensure more variables are present would make it harder to tell which factor is causing any change. Aiming to measure the maximum effect isn’t the point; the goal is to determine whether an effect exists compared to baseline.