In research, what is the purpose of a placebo group?

The purpose of a placebo group in research is to provide a baseline for comparison. This group is crucial for evaluating the effectiveness of a treatment or intervention being tested. In experimental studies, particularly those involving new medical treatments or psychological interventions, participants in the placebo group receive an inert substance or an intervention that has no therapeutic effect, allowing researchers to observe the difference in outcomes between the treatment group and those not receiving the actual treatment.

By having a placebo group, researchers can determine whether the effects observed in the treatment group are truly due to the intervention itself or if they can be attributed to psychological factors, such as the participants' expectations of improvement—what's often referred to as the placebo effect. This comparison helps to eliminate biases and control for confounding variables, ensuring that the results are attributable to the treatment rather than extraneous influences.

The other options do not accurately describe the primary function of a placebo group. Intervening to alter results is contrary to the objective of conducting unbiased research, increasing sample size does not pertain specifically to the role of a placebo, and gathering qualitative data typically focuses on descriptive insights rather than the comparative analysis that a placebo group provides.