Traditionally, women and minorities have not been fully represented in science and engineering. Numerous studies have attributed these differences to gaps in science achievement as measured by various standardized tests. Rather than describe mean group differences in science achievement across multiple cultures, this study focused on an in-depth…

In this study, the Rasch rating scale model (Andrich, 1978) was applied to college grades of four freshman cohorts from a large public university. After editing, the data represented approximately 34,000 students, 1,700 courses and 119 departments. The rating scale model analysis yielded measures of student achievement and course difficulty.…

There are at least two procedures to assess item difficulty stability in the Rasch model: robust z procedure and "0.3 Logit Difference" procedure. The robust z procedure is a variation of the z statistic that reduces dependency on outliers. The "0.3 Logit Difference" procedure is based on experiences in Rasch linking for tests developed by…

Proposes formulas for expected true-score measures and reliability of binary items as a function of their Rasch difficulty when the trait (ability) distribution is normal or logistic. Provides an illustrative example for using the proposed formulas. (SLD)

Studied item calibration stability in relation to response time and the levels of item difficulty between different response groups on a sample of 389 examinees responding to 6 subtest items of the Perceptual Ability Test of the Dental Admission Test. Results show that scores were equally useful for all groups, and different sources of item…

Describes an extension to the Rasch model for fundamental measurement in which there is parameterization not only for examinee ability and item difficulty but also for judge severity. Discusses variants of this model and judging plans, and explains its use in an empirical testing situation. (SLD)

Examined the role that gender differences play in the determination of the components influencing the difficulty of spatial ability items. Results for 2,245 examinees taking a spatial ability test that is part of the Dental School Admission Battery show that component difficulties show little variation across gender. (SLD)

Studied five factors that can affect the equating of scores from two tests onto a common score scale through the simulation and equating of 4,860 item data sets. Findings indicate three statistically significant two-way interactions for common item length and test length, item difficulty standard deviation and item distribution type, and item…