The Nominal Categories Item Response Model
David Thissen, Li Cai, R. Darrell Bock · 2015
The Original Context The nominal categories model (Bock, 1972, 1997) was originally proposed shortly after Samejima (1969, 1997) described the first general item response theory (IRT) model for polytomous responses. Samejima’s graded models (in normal ogive and logistic form) were designed for item responses that have some a priori order as they relate to the latent variable beingmeasured (θ); the nominal model was designed for responses with no predetermined order.