An Assessment of the Dimensionality of Three SAT-Verbal Test Editions

Abstract

A strong assumption made by most commonly used item response theory (IRT) models is that the data are unidimensional, that is, statistical dependence among item scores can be explained by a single ability dimension. First-order and second-order factor analyses were conducted on correlation matrices among item parcels of SAT-Verbal items. The item parcels were constructed to yield correlation matrices that were amenable to linear factor analyses. The first-order analyses were employed to assess the effective dimensionality of the item parcel data. Second-order analyses were employed to test meaningful hypotheses about the structure of the data. Parcels were constructed for three SAT-Verbal editions. The dimensionality analyses revealed that one SAT-Verbal test edition was less parallel to the other two editions than these other editions were to each other. Refinements in the dimensionality methodology and a more systematic dimensionality assessment are logical extensions of the present research.