Standard Errors of Item Parameter Estimates in Incomplete Designs

Lord and Wingersky (1985) derived the asymptotic variance-covariance matrix for item and person param eters in item response models, using maximum likeli hood estimation. Their results can be used in incom plete designs, in which different test forms with common subtests are administered to different groups of examinees. It is also possible to estimate the accu racy 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.