Item response theory (IRT) is a psychometric technique used in the development, evaluation, improvement, and scoring of multi-item scales. This pedagogical article provides the necessary information needed to understand how to conduct, interpret, and report results from two commonly used ordered polytomous IRT models (Samejima’s graded response [GR] model and reduced GR model). Throughout this article, simulated data from a multi-item scale is used to illustrate IRT analyses. The simulated data and IRTPRO version 2.1 point-and-click commands needed to reproduce all analyses in this article are available as supplemental online materials at http://jea.sagepub.com/maint . The intent of this article is to provide an overview of essential components of an IRT analysis to enable increased access to this powerful tool for applied early adolescence researchers.
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