Test control is a process used to evaluate the quality of a product or service. It involves comparing the results of a test against a set of predetermined criteria. The term 'test control' is often used in the context of medical research, where it refers to the use of a PLACEBO as a control group in order to measure the effectiveness of a treatment. A PLACEBO is an inactive substance or procedure that is used as a comparison to measure the effectiveness of a drug or other treatment.