Item parameters: the output of <code>est</code>, or a 3-column matrix 
corresponding to its first element, <code>est</code>.

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

A collection of functions useful in learning and practicing IRT,
which can be combined into larger programs. Provides basic CTT analysis,
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), ability estimation (MLE, BME, EAP, WLE, plausible
values), item and person fit statistics, scaling methods (MM, MS, Stocking-Lord,
and the complete Hebaera method), and a rich array of parametric and
non-parametric (kernel) plots. Estimates and plots Haberman's interaction model
when all items are dichotomously scored.

trf: Test response function

Description

Usage

Arguments

Value

Details

See Also

Examples