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Fitting a Response Model for n Dichotomously Scored Items

Published online by Cambridge University Press:  01 January 2025

R. Darrell Bock
Affiliation:
University of Chicago
Marcus Lieberman
Affiliation:
Institute for Educational Research, Downers Grove, Illinois

Abstract

A method of estimating the parameters of the normal ogive model for dichotomously scored item-responses by maximum likelihood is demonstrated. Although the procedure requires numerical integration in order to evaluate the likelihood equations, a computer implemented Newton-Raphson solution is shown to be straightforward in other respects. Empirical tests of the procedure show that the resulting estimates are very similar to those based on a conventional analysis of item “difficulties” and first factor loadings obtained from the matrix of tetrachoric correlation coefficients. Problems of testing the fit of the model, and of obtaining invariant parameters are discussed.

Information

Type
Original Paper
Copyright
Copyright © 1970 The Psychometric Society

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