When using IRT models in Educational Achievement Testing, the model is as a rule too simple to catch all the relevant dimensions in the test. It is argued that a simple model may nevertheless be useful but that it can be complemented with additional analyses. Such an analysis, called profile analysis, is proposed and applied to the reading data of…

Spearman's factor-analytic model has been proposed as a unidimensional linear item response theory (IRT) model for continuous item responses. This article first proposes a reexpression of the model that leads to a form similar to that of standard IRT models for binary responses and discusses the item indices of difficulty discrimination and…

This study linked nonlinear profile analysis (NPA) of dichotomous responses with an existing family of item response theory models and generalized latent variable models (GLVM). The NPA method offers several benefits over previous internal profile analysis methods: (a) NPA is estimated with maximum likelihood in a GLVM framework rather than…

Investigated the usefulness of multidimensional scaling (MDS) for assessing the dimensionality of dichotomous test data. Focused on two MDS proximity measures, one based on the PC statistic (T. Chen and M. Davidson, 1996) and other, on interitem Euclidean distances. Simulation results show that both MDS procedures correctly identify…

The valid provision of subscores from an item response theory-based test implies a multidimensional test structure. Assuming, in the construction of a new test, that the test features required for a valid and reliable total test score have been specified already, this article describes the resulting subscore performance and the resulting…

In this paper I describe and illustrate the Roussos-Stout (1996) multidimensionality-based DIF analysis paradigm, with emphasis on its implication for the selection of a matching and studied subtest for DIF analyses. Standard DIF practice encourages an exploratory search for matching subtest items based on purely statistical criteria, such as a…

A new method for evaluating the content representation of a test is illustrated. Item similarity ratings were obtained from three content domain experts to assess whether ratings corresponded to item groupings specified in the test blueprint. Multidimensional scaling and cluster analysis provided substantial information about the test's content…

This study compared four methods for setting item response time thresholds to differentiate rapid-guessing behavior from solution behavior. Thresholds were either (a) common for all test items, (b) based on item surface features such as the amount of reading required, (c) based on visually inspecting response time frequency distributions, or (d)…

Many researchers have suggested that the main cause of item bias is the misspecification of the latent ability space. That is, items that measure multiple abilities are scored as though they are measuring a single ability. If two different groups of examinees have different underlying multidimensional ability distributions and the test items are…

Academic psychology has long been composed of two disciplines, one experimental and one correlational. These two disciplines each developed their own method of studying structure in data: multidimensional scaling (MDS) and factor analysis. Both methods use similar kinds of input data, proximity measures on object pairs. Both represent the object…

The problem of dimensionality with respect to Raven's Advanced Progressive Matrices (APM) specifically and, more generally, "g" or fluid intelligence, has been a long-standing issue. The present article reports two studies examining the dimensionality of both the original Set II of the APM (n = 506) and a short form (n = 644), using principal…

Many researchers have suggested that the cause of differential item functioning (DIF) can in part be due to the misspecification of the supporting trait distribution (STD). This paper demonstrates how a unidimensional item response theory (IRT) calibration of response data, generated from a two-dimensional IRT model, results in DIF when the…

The concept of a user-specified validity sector is discussed. The idea of the validity sector combines the work of M. D. Reckase (1986) and R. Shealy and W. Stout (1991). Reckase developed a methodology to represent an item in a multidimensional latent space as a vector. Item vectors are computed using multidimensional item response theory item…

One of the major assumptions of latent trait theory is that the items in a test measure a single dimension. This report describes an investigation of procedures for forming a set of items that meet this assumption. Factor analysis, nonmetric multidimensional scaling, cluster analysis and latent trait analysis were applied to simulated and real…

An expanded version of the method of content evaluation proposed by S. G. Sireci and K. F. Giesinger (1992) was evaluated with respect to a national licensure examination and a nationally standardized social studies achievement test. Two groups of 15 subject-matter experts rated the similarity and content relevance of the items. (SLD)