Abstract

The statistical foundation of item response theory (IRT) is often traced back to the seminal work of Lord, Novick, and Birnbaum (1968). The subsequent development, research, and application of IRT models and related methods link directly to the need of large-scale testing companies, such as the Educational Testing Service, to solve statistical as well as practical problems in educational assessment (i.e., the measurement of aptitude, achievement, and ability constructs). Daunting problems in this include the challenge of administering different test items to demographically diverse individuals across multiple years, while maintaining scores that are comparable on the same scale. This test score comparability problem traditionally has been addressed with “test-score equating” methods, but now more routinely, IRT-based “linking” strategies are used (see Chapter 19).