posteriorKL {catSurv} R Documentation

## Expected Kullback-Leibler Information, Weighted by the Prior

### Description

Calculates the expected Kullback-Leibler information, weighted by likelihood and prior beliefs, for a specified item.

### Usage

posteriorKL(catObj, item)


### Arguments

 catObj An object of class Cat item An integer indicating the index of the question item

### Details

The function posteriorKL calculates the expected Kullback-Leibler information for question item, where the proposed values of the true ability parameter are weighted by the prior.

### Value

The function posteriorKL returns a numeric indicating the expected Kullback-Leibler information weighted by the likelihood for the specified item, given the current answer profile and ability parameter estimate.

### Note

This function is to allow users to access the internal functions of the package. During item selection, all calculations are done in compiled C++ code.

This function uses adaptive quadrature methods from the GNU Scientific Library (GSL) to approximate single-dimensional integrals with high accuracy. The bounds of integration are determined by the lowerBound and upperBound slots of the Cat object.

### Author(s)

Haley Acevedo, Ryden Butler, Josh W. Cutler, Matt Malis, Jacob M. Montgomery, Tom Wilkinson, Erin Rossiter, Min Hee Seo, Alex Weil

expectedKL, likelihoodKL, selectItem

### Examples

## Loading ltm Cat object
data(ltm_cat)