In psychometrics, item response theory (IRT) also known as latent trait theory, strong true score theory, or modern mental test theory, is a paradigm for the design, analysis, and scoring of tests, questionnaires, and similar instruments measuring abilities, attitudes, or other variables. It is based on the application of related mathematical models to testing data. Because it is generally regarded as superior to classical test theory, it is the preferred method for the development of high-stakes tests such as the Graduate Record Examination (GRE) and Graduate Management Admission Test (GMAT).

Die Probabilistische Testtheorie (Item Response Theory) beschreibt, wie man aus Ergebnissen standardisierter psychometrischer Tests auf Persönlichkeitseigenschaften zurückschließen kann.