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

• A. It provides a baseline to compare outcomes without the independent variable.
• B. It ensures randomization of participants in the study.
• C. It guarantees the treatment will work in all subjects.
• D. It speeds up data collection.

Answer: (A)

Having a control group provides a baseline for comparison so you can see what happens without the independent variable. By measuring both groups under the same conditions, any difference in outcomes can be attributed more confidently to the treatment itself rather than chance, natural variation, or external factors. This setup helps determine whether the observed effect is real and not just a fluke. The control group isn’t about guaranteeing the treatment works in everyone or speeding up data collection; those are separate considerations. Randomization can help balance other variables across groups, but the essential purpose of the control group is to establish a standard to judge the treatment’s effect.