A placebo-controlled research study is a type of experiment in which participants are randomly assigned to receive either a treatment (e.g. medication, therapy) or a placebo (e.g. sugar pill, inactive substance). The purpose of this design is to investigate the effectiveness of the treatment by comparing outcomes in the group receiving the treatment to those in the group receiving the placebo. This type of study helps researchers determine if the treatment has a genuine effect beyond the placebo effect, which is a psychological phenomenon where a person experiences improvement in symptoms simply because they believe they are receiving treatment. Placebo-controlled studies are considered the gold standard in clinical research for evaluating the efficacy and safety of new interventions.