In experimental designs, the control group primarily serves to

• A. Generalize results
• B. Provide a baseline to estimate the effect of the intervention by controlling for confounding variables
• C. Increase sample size
• D. Improve instrument reliability

Answer: (B)

The main idea is that a control group provides a baseline for what would happen without the intervention, so you can estimate the intervention’s effect by comparing groups that are treated the same except for the treatment. By keeping conditions and other factors the same, differences in outcomes can be attributed to the intervention rather than confounding variables like natural variation, placebo effects, or external events. This setup strengthens internal validity and helps separate the true effect of the treatment from other influences. The other options describe other study goals, but they aren’t the primary function of the control group.