Explanatory IRT Analysis Using the SPIRIT Macro in SPSS

Abstract

Item Response Theory (IRT) is a modeling framework that can be applied to a large va- riety of research questions spanning several disciplines. To make IRT models more accessible for the general researcher, a free tool has been created that can easily conduct one-parameter logis- tic IRT (1PL) analyses using the convenient point-and-click interface in SPSS without any required downloads or add-ons. This tool, the SPIRIT macro, can fit 1PL models with person and item covari- ates, DIF analyses, multidimensional models, multigroup models, rating scale models, and several other variations. Example explanatory models are presented with an applied dataset containing responses to an ADHD rating scale. Illustrations of how to fit basic 1PL models as well as two more complicated analyses using SPIRIT are given.