What is the purpose of a control group?

• A. To test a treatment under controlled conditions
• B. To serve as a baseline for comparison
• C. To calibrate instruments
• D. To maximize variables

Answer: (B)

The main idea is that a control group provides a baseline for comparison. By not receiving the experimental treatment (or by receiving a standard or placebo), this group shows what happens without the new intervention, so any observed differences can be attributed to the treatment itself rather than other factors. This setup helps account for natural variation and placebo effects, making it clearer whether the treatment really has an effect. The other choices don’t fit: testing a treatment under controlled conditions refers to the experimental group, calibrating instruments is about measurement accuracy, and maximizing variables would introduce more uncontrolled factors rather than establish a baseline.