What is the purpose of a control group in experiments?

• A. A control group provides a baseline for comparison to isolate the effect of the IV and control non-specific factors.
• B. A control group ensures participants receive the experimental treatment.
• C. A control group eliminates all variability in the data.
• D. A control group guarantees random sampling.

Answer: (A)

The main idea is that a control group provides a baseline for comparison so you can see what happens without the experimental manipulation and then determine whether the independent variable is driving any observed effects. By keeping everything between the control and experimental groups as similar as possible, except for the IV, you can attribute differences in outcomes to the manipulation rather than to other factors like placebo responses, expectations, or natural changes over time. The control group does not receive the experimental treatment, which is what allows that clean comparison. The other options don’t fit because providing the treatment is the role of the experimental group, not the control; eliminating all variability isn’t achievable and isn’t the function of a control group; random sampling is a sampling issue, not the purpose of having a control condition (random assignment relates to how participants are placed into groups).