Investigated how well the generalized and Rasch models described item and test performance across a broad range of mixed-item-format test configurations (six tests from two state proficiency testing programs). Evaluating the impact of model assumptions on the predictions of item and test information permitted a delineation of the implications of…

Two methods of constucting equal-interval scales for educational achievement are discussed: Thurstone's absolute scaling method and Item Response Theory. Alternative criteria for choosing a scale are contrasted. It is argued that clearer criteria are needed for judging the appropriateness and usefulness of alternative scaling procedures.…

A study of the context effects on item parameters for one- and three-parameter latent trait models showed that: (1) changes in context affected their item difficulties; and (2) context effects were more important in making predictions for single items than for groups of items. (Author/RL)

A procedure for obtaining maximum likelihood trait estimates from number-correct (NC) scores for the three-parameter logistic model is presented. It produces an NC score to trait estimate conversion table. Analyses in the estimated true score metric confirm the conclusions made in the trait metric. (Author/DWH)