InformationLocation: Location of each item's maximum information

In CambridgeAssessmentResearch/unimirt: Applications of Unidimensional IRT using the R Package 'mirt'

Location of each item's maximum information

Description

This function calculates the ability value at which each item has the highest value for its information function. For dichotomous items this will usually be the same as the item difficulty parameter. For polytomous items it may provide an idea of the point in the ability scale where the item is most useful.

Usage

InformationLocation(mirtobj, which.items = NULL)

Arguments

mirtobj	An estimated IRT model (of class SingleGroupClass) estimated using mirt or unimirt.
which.items	an integer vector indicating which items to include. By default all items are included.

Value

A data frame of item names, item maxima and theta locations of maximum information.

Examples

## Not run: 
#model using "Science" data from mirt package
scimod=unimirt(Science[,1:4]-1,"gpcm")
InformationLocation(scimod)
#visual verification
unimirt.plot(scimod,"infotrace")

## End(Not run)

CambridgeAssessmentResearch/unimirt documentation built on June 10, 2025, 6:03 a.m.