Standard errors of item parameter estimates in incomplete designs

Abstract

Lord and Wingersky (1985) derived the asymptotic variance-covariance matrix for item and person parameters in item response models, using maximum likelihood estimation. Their results can be used in incomplete designs, in which different test forms with common subtests are administered to different groups of examinees. It is also possible to estimate the accuracy of various designs beforehand, which enables the researcher to select the best of several designs under consideration. The possibilities are demonstrated for the one- and two-parameter models. Index terms: Asymptotic standard errors, Incomplete designs, Item banking, Information matrix, Maximum likelihood, Rasch model, Two-parameter logistic model.