Item Response Theory

Item response theory (IRT) is an increasingly popular approach to the development, evaluation, and administration of psychological measures. We introduce, first, three IRT fundamentals: (a) item response functions, (b) information functions, and (c) invariance. We next illustrate how IRT modeling can improve the quality of psychological measurement. Available evidence suggests that the differences between IRT and traditional psychometric methods are not trivial; IRT applications can improve the precision and validity of psychological research across a wide range of subjects.