Which group lacks what is being tested and is used to provide the expected results?

• A. Experimental group
• B. Positive control group
• C. Negative control group
• D. Treatment group

Answer: (C)

The main idea here is how controls establish a baseline to interpret results. A negative control group is the one that does not receive the factor being tested. Because it lacks the tested variable, any outcome you observe in this group reflects background signals, noise, or spontaneous changes rather than the effect of the treatment. This baseline is what you compare other groups against to determine if the intervention truly produced a difference. For example, in a drug study, the negative control might receive a placebo, so you expect no therapeutic effect and you can attribute any difference in the treated groups to the drug itself. In contrast, a positive control is given a known active treatment to confirm the system can respond, ensuring the experiment can detect an effect if there is one. The groups that actually receive the test variable—the experimental or treatment group—are the ones used to measure the effect of interest.