The accuracy of a test in making a dichotomous classification might be evaluated by one of four related statistics. Of these four statistics, specificity is used to evaluate the probability of correctly identifying the absence of some condition or disease state. For example, specificity might be used in a medico-legal setting to describe that a particular test has 95% probability of detecting that a head-injured patient is not malingering. Specificity is calculated as the proportion of true negative cases divided by all cases without the condition.