infutil (version 1.0)

iota.l: Lindley Information (i.e., Information Utility) Lower Bound

Description

This function calculates the lower bound to the Lindley information (i.e., information utility) given a Jeffreys prior normalizing constant or ltm object.

Usage

iota.l(x)

Arguments

x

Either an ltm object or a Jeffreys prior normalizing constant. x can be a scalar or vector.

Value

A lower bound to the Lindley information, or a vector of lower bounds for different sets of items.

Details

This function calculates the lower bound to the Lindley information (i.e., information utility) given a Jeffreys prior normalizing constant or ltm object.

x can be an object from the ltm package describing a set of IRT parameters (e.g., as returned by ltm, grm, or gpcm).

If x is a vector, the function will return a vector of lower bounds.

References

Markon, K. E. (2013). Information utility: Quantifying the total psychometric information provided by a measure. Psychological Methods, 18, 15-35. doi: 10.1037/a0030638..

See Also

Jeffreys, iota.c, nmru, iota, ltm, grm, gpcm

Examples

ltm.lsat <- ltm(LSAT~z1, IRT=FALSE)

iota.l(ltm.lsat)
iota.l(Jeffreys(ltm.lsat, return="nc"))