Sensitivity is one of four related statistics used to describe the accuracy of an instrument for making a dichotomous classification (i.e., positive or negative test outcome). Of these four statistics, sensitivity is defined as the probability of correctly identifying some condition or disease state. For example, sensitivity might be used in medical research to describe that a particular test has 80% probability of detecting anabolic steroid use by an athlete. This entry describes how sensitivity scores are calculated and the role of sensitivity in research design.