information {ltm}R Documentation

Area under the Test Information Function

Description

Computes the amount of test information for a fitted IRT model, in a specified range.

Usage

information(object, range, items = NULL, ...)

Arguments

object an object inheriting from either class grm, class ltm or class rasch.
range a numeric interval for which the test information should be computed.
items the items for which the information should be computed; the default NULL corresponds to all the items, which is equivalent to the test information.
... extra arguments passed to integrate().

Details

The amount of information is computed as the area under the Item or Test Information Curve in the specified interval, using integrate().

Value

A list with components,

Info in range the amount of information in the specified interval.
Total Info the total amount of information; typically this is computed as the amount of information in the interval (-10, 10).
Proportion in range the proportion of information in the specified range, i.e., "Info in range" / "Total Info".

Author(s)

Dimitris Rizopoulos dimitris.rizopoulos@med.kuleuven.be

See Also

plot.grm, plot.ltm, plot.rasch

Examples


m <- rasch(Lsat)
information(m, c(-2, 0))
information(m, c(0, 2), items = 3)


[Package ltm version 0.4-1 Index]