Item Response Theory (from: 9th edition of Psychological testing and assessment) - Cohen - Article
1. Item Response Theory (Cohen)
Item Response Theory (IRT), also known as latent-trait theory, is a family of theories and methods that provides a way to model the probability that a person with X ability (e.g., a particular personality trait) is able to perform (e.g., on a personality test) at a level of Y.
IRT is not a single method or theory. Instead, IRT is a family of theories and methods, comprising well over a hundred different models. Each model as its own assumptions and data characteristics to handle data. There are, for instance, IRT models designed specifically for tests with dichotomous test items (yes/no, true/false). Other models are specifically designed to for tests polytomous items (test items with three or more answer categories). Another important group of IRT models is developed by the Danish mathematician George Rash. He developed the so-called Rasch model in which each item on
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