The role of a control in an experiment is to

• A. Provide a basis of comparison to the experimental group.
• B. Provide randomization to reduce bias.
• C. Ensure identical results every time.
• D. Prove the hypothesis.

Answer: (A)

The main idea is that a control provides a baseline for comparison. By keeping all factors the same between the control group and the experimental group except for the independent variable, you can see whether the treatment itself causes any difference in the outcome. This helps attribute observed effects specifically to what you’re testing rather than to other variables.

In a well-designed experiment, the control lets you answer: would the same result occur without the experimental treatment? If the experimental group shows a different outcome from the control, you can infer that the independent variable had an effect.

Randomization helps reduce bias during group assignment, but that’s about how subjects are chosen and assigned, not the control’s primary role. Controls do not guarantee identical results every time, since natural variability exists. And a control by itself does not prove the hypothesis; it provides a baseline that, when compared with the experimental group, helps evaluate the hypothesis. For example, in a drug trial, a placebo control shows whether improvements are due to the drug or to other factors like placebo effects.