R: Area under the Test or Item Information Curves

information {ltm}

R Documentation

Area under the Test or Item Information Curves

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

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

`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()`.

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

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`.


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

[Package ltm version 1.2-0 Index]