The term false positive is most commonly employed in diagnostic classification within the context of assessing test validity. The term represents a diagnostic decision in which an individual has been identified as having a specific condition (such as an illness), when, in fact, he or she does not have the condition. The term false positive is less commonly used within the context of hypothesis testing to represent a Type I error, which is defined as rejection of a true null hypothesis, and thereby incorrectly concluding that the alternative hypothesis is supported. This entry focuses on the more common use of the term false positive within the context of diagnostic decision making. The disciplines that are most likely to be concerned with the occurrence of false ...