An individual case is considered matched in a sample when it possesses similar attributes to another case in the sample. Matching can be used to reduce or eliminate confounding within an experiment. When matching is utilized in a study, the researcher matches the attributes of a case with another case in the sample and applies a treatment and control to each pair of matched individuals. There are both advantages and disadvantages to utilizing a matched individuals sampling technique, as well as the possibility to overmatch individuals within a sample. This entry discusses how individuals are matched in a sample, why researchers should or should not use a matched individuals sampling technique in their research, and some of the issues that surround overmatching within a sample. ...