expected.item: Function to calculate expected value of item

In xzhaopsy/MIRT: Multidimensional Item Response Theory

Description

Given an internal mirt object extracted from an estimated model compute the expected value for an item given the ability parameter(s).

Usage

expected.item(x, Theta, min = 0)

Arguments

x	an extracted internal mirt object containing item information (see extract.item)
Theta	a vector (unidimensional) or matrix (multidimensional) of latent trait values
min	a constant value added to the expected values indicating the lowest theoretical category. Default is 0

Author(s)

Phil Chalmers [e-mail]

References

Chalmers, R., P. (2012). mirt: A Multidimensional Item Response Theory Package for the R Environment. Journal of Statistical Software, 48(6), 1-29. doi: 10.18637/jss.v048.i06

See Also

extract.item, expected.test

Examples

## Not run: 
mod <- mirt(Science, 1)
extr.2 <- extract.item(mod, 2)
Theta <- matrix(seq(-6,6, length.out=200))
expected <- expected.item(extr.2, Theta, min(Science[,1])) #min() of first item
head(data.frame(expected, Theta=Theta))


## End(Not run)

xzhaopsy/MIRT documentation built on May 29, 2019, 12:42 p.m.