Functional Approaches for Modeling Unfolding Data

The purpose of this study is to introduce a functional approach for modeling unfolding response data. Functional data analysis (FDA) has been used for examining cumulative item response data, but a functional approach has not been systematically used with unfolding response processes. A brief overview of FDA is presented and illustrated within the context of unfolding data. Seven decision parameters are described that can provide a guide to conducting FDA in this context. These decision parameters are illustrated with real data using two scales that are designed to measure attitude toward capital punishment and attitude toward censorship. The analyses suggest that FDA offers a useful set of tools for examining unfolding response processes.