A double-blind test is a scientific method of testing where neither the tester nor the participant has knowledge about the assigned treatment. This technique is used to eliminate the bias and increase the reliability of the results obtained. There are several other terms used as synonyms of a double-blind test, such as a placebo-controlled study, randomized controlled trial, masked study, parallel study, and blinded trial. Each of these terms has a slight variation in its usage, but they all refer to the same concept of conducting research without any preconceived notions or bias. Double-blind tests have proven to be an effective way of producing accurate data and are widely used in medical and scientific research.