Some Empirical Results Related to the Robustness of the Rasch Model

The primary purpose of this study was to investigate the invariance properties of the Rasch model using data from standardized achievement tests that were not constructed to conform to the Rasch model. The item responses of approximately '3,400 examinees (Grades 9, 10, 11, and 12) to four separately timed sections of the Iowa Tests of Educational Development were analyzed. The re sults indicated that the Rasch model does yield rea sonably invariant item parameter and ability parameter estimates for different tests and different examinee groups, even though the assumptions of the model are not met.