What defines a "control group" in research?

A control group is fundamentally characterized as a group of participants that does not receive the experimental treatment, serving as a benchmark against which the effects of the treatment can be measured. This allows researchers to isolate the effects of the experimental treatment by comparing results between the control group and the treatment group. By not receiving the treatment, the control group helps to account for variables that could influence the outcome, such as the placebo effect or changes over time that could affect all participants.

This comparison is crucial for establishing the effectiveness of the experimental treatment. It enables researchers to draw more accurate conclusions about whether the changes observed in the experimental group are indeed due to the treatment itself or other external factors.

In contrast, a group that receives the experimental treatment is specifically the treatment group, while a randomly selected group does not inherently serve the purpose of a control group, as random selection pertains more to sampling methods than to groups defined by treatment. A group receiving a placebo might also function as a control group, but that is a specific case of the broader definition that includes any non-treatment comparison group.