A controlled trial is a type of scientific study in which a specific intervention or treatment is tested by comparing it against a control group that does not receive the intervention. This allows researchers to determine if the intervention has a significant impact on the outcome being studied. Controlled trials are often used in medical research to evaluate the effectiveness of new treatments or interventions in a controlled and systematic way. By comparing the results of the intervention group to the control group, researchers can determine whether the intervention is effective and potentially recommend its use in clinical practice.