Item parameters: a matrix with one row per
  item, and three columns: [,1] item discrimination
  $a$, [,2] item difficulty $b$, and [,3] asymptote
  $c$.

The values of the latent variable ($\theta$
  in the equation above), at which the IRF will be
  evaluated. If not given, 99 values spaced evenly between
  -4 and +4 will be used, handy for plotting.


  Returns the test response function (TRF) of the 3PL (1PL,
  2PL) model. The TRF is the sum of the item response
  functions (IRF) in a test, and represents the expected
  score as a function of the latent variable $\theta$.


models

Provides a simple common interface to the estimation of item
parameters in IRT models for binary responses with three different programs
(ICL, BILOG-MG, and ltm, and a variety of functions useful with IRT models.

trf: Test response function

Description

Usage

Arguments

Value

Details

See Also

Examples