likelihoodKL function

Expected Kullback-Leibler Information, Weighted by Likelihood

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

likelihoodKL(catObj, item)

Arguments

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

Returns

The function likelihoodKL 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.

Details

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

This function involves integration. See Note for more information.

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.

Examples

## Loading ltm Cat object
data(ltm_cat)

## Store example answers
setAnswers(ltm_cat) <- c(1,0,1,0,1, rep(NA, 35))

## Estimate EPV for different unasked items
likelihoodKL(ltm_cat, item = 10)
likelihoodKL(ltm_cat, item = 20)
likelihoodKL(ltm_cat, item = 30)

See Also

expectedKL, posteriorKL, selectItem

Author(s)

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