Statistical Bias in Maximum Likelihood Estimators of Item Parameters IRT

Author(s):

Lord, Frederic M.

Publication Year:

1982

Report Number:

RR-82-20

Source:

ETS Research Report

Document Type:

Report

Page Count:

10

Subject/Key Words:

Office of Naval Research, Error of Measurement, Item Response Theory (IRT), Mathematical Formulas, Maximum Likelihood Statistics, Statistical Analysis, Test Bias

Abstract

Formulas are derived for the bias in the maximum likelihood estimators (MLE) of the item parameters in the logistic item response model when examinee abilities are known. Numerical results are given for a typical verbal test for college admission. Most typically the bias of an MLE is about one-tenth of its standard error. It is very seldom more than a fifth of its standard error. The effect of bias for individual item-parameter estimates is thus probably negligible. (Author/PN). (10pp.)

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• http://dx.doi.org/10.1002/j.2333-8504.1982.tb01306.x