A Factor-Analytic Model for Assessing Individual Differences in Response Scale Usage.

This article proposes a factor-analytic model, intended for graded-response or continuous-response personality and attitude items, which includes an additional multiplicative person parameter that models the individual's response mapping process. The model, which is a modification of Spearman's (1904) factor analysis (FA) model, is parameterized as both an FA model and an item response theory (IRT) model and is fully developed to the extent that it can be used in applications. Procedures for (a) calibrating the items and assessing data fit, (b) obtaining individual estimates of both person parameters, (c) determining measurement precision, and (d) assessing differential predictability are proposed and discussed. The potential advantages of the proposal, its practical relevance, and its relations with other approaches are also discussed. Its functioning is assessed with a simulation study and 3 empirical examples in the personality domain.