An Ordinal Item Response Model for Understanding Attitudes

Abstract

We present an item response model for ordinal public opinion data to understand individual-level variation in attitudes as a function of covariates. The approach allows investigating how individuals (or population subgroups) differ in substantive stances and attitude strength. It is a two-dimensional partial credit model that incorporates covariates linked to attitude direction and strength into the basic model. We exemplify the types of substantive insights into heterogeneity that can be obtained from the approach but not from existing models with two applications: attitudes toward gender equality (European Values Study) and the evaluation of presidential candidates (American National Election Study).