An Intellectual History of Parametric Item Response Theory Models in the Twentieth Century

The intellectual history of parametric item response theory (IRT) models is traced from ideas that originated with E.L. Thorndike, L.L. Thurstone, and Percival Symonds in the early twentieth century. Gradual formulation as a set of latent vari- able models occurred, culminating in publications by Paul Lazarsfeld and Federic Lord around 1950. IRT remained the province of theoreticians without practical ap- plication until the 1970s, when advances in computational technology made possible data analysis using the models. About the same time, the original normal ogive and simple logistic models were augmented with more complex models for multiple- choice and polytomous items. During the final decades of the twentieth century, and continuing into the twenty-first, IRT has become the dominant basis for large-scale educational assessment.