information: Area under the Test or Item Information Curves

In ltm: Latent Trait Models under IRT

Area under the Test or Item Information Curves

Description

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

Usage

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

Arguments

object	an object inheriting from either class gpcm, class grm, class ltm, class rasch or class tpm.
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 of class information with components,

InfoRange	the amount of information in the specified interval.
InfoTotal	the total amount of information; typically this is computed as the amount of information in the interval (-10, 10).
PropRange	the proportion of information in the specified range, i.e., "Info in range" / "Total Info".
range	the value of range argument.
items	the value of items argument.
call	the matched call for object.

Author(s)

Dimitris Rizopoulos [e-mail]

See Also

plot.gpcm, plot.grm, plot.ltm, plot.rasch

Examples

fit <- rasch(LSAT)
information(fit, c(-2, 0))
information(fit, c(0, 2), items = c(3, 5))

ltm documentation built on March 18, 2022, 6:36 p.m.