OscatsModelL3p

OscatsModelL3p — Three-Parameter Logistic (3PL) Model

Synopsis

struct              OscatsModelL3p;

Object Hierarchy

  GObject
   +----OscatsModel
         +----OscatsModelL3p

Description

Details

struct OscatsModelL3p

struct OscatsModelL3p;

The Three-Paramter Logistic IRT model: P(X=1|theta) = c + (1-c)/1+exp[-(sum_i a_i theta_i -b + sum_j d_j covariate_j)], where a_i are the item discrimination for each dimension and b is the scaled item difficulty. Note that this differs from the usual IRT parameterization c + (1-c)/1+exp[-a(theta-b)]. Distance is defined as: abs(sum_i a_i theta_i - b + sum_j d_j covariate_j).

Parameter names: Diff, Guess, Discr.DimName

References:

R. J. de Ayala (2009). The Theory and Practice of Item Response Theory. p 124, 288.

A. Birnbaum (1968). "Some Latent Trait Models and Their Use in Inferring an Examinee's Ability." In F. M. Lord and M. R. Novick. Statistical Theories of Mental Test Scores p 405.