How accurately ability is estimated when the test model does not fit the data is considered. To address this question, this study investigated the accuracy of the maximum likelihood estimator of ability for the one-, two- and three-parameter logistic (PL) models. The models were fitted into generated item characteristic curves derived from the…

Heckman's correction for regression in selected samples for predictive validity studies was applied to a large data file on 7,984 law school applicants. Data included ethnic group, sex, socioeconomic status, undergraduate degree, school, scores on the Law School Admission Test (LSAT), writing ability, undergraduate grade point average, and age.…

It is suggested that bias--when associated with a predictor, a test, or a statistical estimator--is not always bad, in spite of the immediate negative response evoked by the word, bias. Four settings are described to illustrate situations in which a procedure should not be summarily rejected due to bias: (1) educational researchers rejected the…