In this study, we contrast results from two differential item functioning (DIF) approaches (manifest and latent class) by the number of items and sources of items identified as DIF using data from an international reading assessment. The latter approach yielded three latent classes, presenting evidence of heterogeneity in examinee response…

International large-scale assessments of achievement often have a large degree of differential item functioning (DIF) between countries, which can threaten score equivalence and reduce the validity of inferences based on comparisons of group performances. It is important to understand potential sources of DIF to improve the validity of future…

In this study, the Canadian English and French versions of the Problem-Solving Measure of the Programme for International Student Assessment 2003 were examined to investigate their degree of measurement comparability at the item- and test-levels. Three methods of differential item functioning (DIF) were compared: parametric and nonparametric item…

This article focuses on Louis Guttman's contributions to the classical theory of educational and psychological tests, one of the lesser known of his many contributions to quantitative methods in the social sciences. Guttman's work in this field provided a rigorous mathematical basis for ideas that, for many decades after Spearman's initial work,…

Agonias is an idiom of distress for Portuguese community members. Although this phenomenon was recently introduced in the mental health literature, a measure for it was not available. The Agonias Scale was introduced in this article and the psychometric properties are reported. The scale was found to have strong psychometric properties of…

Developed an item characteristic curve estimation of signal detection theory based personality data. Results for 266 college students taking the Overclaiming Questionnaire (D. Paulhus and N. Bruce, 1990) suggest that this method is a reasonable approach to describing item functioning and that there are advantages to this method over traditional…

Presents a model of tests and measurement that identifies test scores with Hilbert space vectors and true and error components of scores with linear operators. This geometric point of view brings to light relations among elementary concepts in test theory, including reliability, validity, and parallel tests. (Author/SLD)