What is the purpose of a control group in experimental research?

The purpose of a control group in experimental research is to provide a baseline for comparison against the treatment group. This allows researchers to determine the effects of the independent variable being tested by comparing the outcomes in the control group, which does not receive the treatment, to those in the treatment group, which does. By having a control group, it becomes possible to attribute differences in outcomes to the treatment itself rather than other external factors or variables.

Having a control group also helps to isolate the effects of the treatment, enhancing the internal validity of the experiment. This is crucial for establishing causality and ensuring that the results are a direct result of the manipulation of the independent variable.

In contrast, introducing additional variables in an experimental design could confound the results and make it difficult to draw clear conclusions about the effects of the treatment. Eliminating bias in sample selection is important, but it is a separate consideration from the role of the control group. Furthermore, ensuring that all participants receive the treatment does not align with the function of a control group, which is specifically designed not to receive the treatment for a fair evaluation.