A Note on a Computationally Efficient Implementation of the EM Algorithm in Item Response Models

Authors

  • Alexander Robitzsch
    IPN – Leibniz Institute for Science and Mathematics Education, Kiel, Germany; Center for International Student Assessment (ZIB), Kiel, Germany

Abstract

This note sketches two computational shortcuts for estimating unidimensional item response models and multidimensional item response models with between-item dimensionality utilizing an expectation-maximization (EM) algorithm that relies on numerical integration with fixed quadrature points. It is shown that the number of operations required in the E-step can be reduced in situations of many cases and many items by appropriate shortcuts. Consequently, software implementations of a modified E-step in the EM algorithm could benefit from gains in computation time.