OscatsModelGpc

OscatsModelGpc — Generalized Partial Credit Model

Synopsis

struct              OscatsModelGpc;

Object Hierarchy

  GObject
   +----OscatsModel
         +----OscatsModelGpc

Properties

  "Ncat"                     guint                 : Read / Write / Construct Only

Description

Details

struct OscatsModelGpc

struct OscatsModelGpc;

The Generalized Partial Credit Model is a special case of Bock's Nominal Response Model (OscatsModelNominal): P(X=k|theta) = f_k(theta)/[1+sum_j f_j(theta)], where f_j(theta) = sum_i a_i theta_i - b_j + sum_l d_l covariate_l, a_i is the discrimination for dimension i, b_j is the scaled option difficulty, and f_0(theta) = 0. Responses are numbered 0, 1, ..., Ncat-1. Note that all options share the same parameters for the covariates. No distance metric is currently provided, but see Ali (2011) for possibilities.

Parameter names: Diff.k, Discr.DimName

References:

R. J. de Ayala (2009). The Theory and Practice of Item Response Theory. p 209-210.

Eiji Muraki (1992). "A Generalized Partial Credit Model: Application of an EM Algorithm." Applied Psychological Measurement, 16, 159-176.

Usama Ali (2011). Item Selection Methods in Polytomous Computerized Adaptive Testing. Dissertation, University of Illinois.

Property Details

The "Ncat" property

  "Ncat"                     guint                 : Read / Write / Construct Only

The number of response categories in the IRT model, numered 0, 1, ..., Ncat-1. The default number of categories is 3, which is also the minimum.

Allowed values: >= 3

Default value: 3