OscatsModelGr

OscatsModelGr — Homogenous Logistic Graded Response Model

Synopsis

struct              OscatsModelGr;

Object Hierarchy

  GObject
   +----OscatsModel
         +----OscatsModelGr

Properties

  "Ncat"                     guint                 : Read / Write / Construct Only

Description

Details

struct OscatsModelGr

struct OscatsModelGr;

The Homogenous Logistic Graded Response IRT model (commonly called simply the Graded Response Model): P(X=k|theta) = P*_k(theta) - P*_{k+1}(theta), P*_k(theta) = 1/1+exp[-(sum_i a_i theta_i - b_k + sum_j d_j covariate_j)] where P*_k(theta) = P(X>=k|theta) is the probability of scoring at least k, P*_0(theta) = 1, P*_{Ncat} = 0, a_i is the discrimination on dimension i, and b_k is the scaled response boundary location. Responses are numbered 0, 1, ..., Ncat-1. Note that all respose 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 217-222.

F. Samejima (1976). "The graded response model of latent trait theory and tailored testing." Proceedings of the First Conference on Computerized Adaptive Testing, 5-15.

F. Samejima (1969). "Estimation of latent ability using a response pattern of graded scores." Psychometrika Monograph Supplement, 17.

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