testinfo: Function to calculate test information

In mirt: Multidimensional Item Response Theory

Function to calculate test information

Description

Given an estimated model compute the test information.

Usage

testinfo(
  x,
  Theta,
  degrees = NULL,
  group = NULL,
  individual = FALSE,
  which.items = 1:extract.mirt(x, "nitems")
)

Arguments

x	an object of class 'SingleGroupClass', or an object of class 'MultipleGroupClass' if a suitable group input were supplied
Theta	a matrix of latent trait values
degrees	a vector of angles in degrees that are between 0 and 90. Only applicable when the input object is multidimensional
group	group argument to pass to extract.group function. Required when the input object is a multiple-group model
individual	logical; return a data.frame of information traceline for each item?
which.items	an integer vector indicating which items to include in the expected information function. Default uses all possible items

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. \Sexpr[results=rd]{tools:::Rd_expr_doi("10.18637/jss.v048.i06")}

Examples

dat <- expand.table(deAyala)
(mirt(dat, 1, '2PL', pars = 'values'))
mod <- mirt(dat, 1, '2PL', constrain = list(c(1,5,9,13,17)))

Theta <- matrix(seq(-4,4,.01))
tinfo <- testinfo(mod, Theta)
plot(Theta, tinfo, type = 'l')

## Not run: 

# compare information loss between two tests
tinfo_smaller <- testinfo(mod, Theta, which.items = 3:5)

# removed item informations
plot(Theta, iteminfo(extract.item(mod, 1), Theta), type = 'l')
plot(Theta, iteminfo(extract.item(mod, 2), Theta), type = 'l')

# most loss of info around -1 when removing items 1 and 2; expected given item info functions
plot(Theta, tinfo_smaller - tinfo, type = 'l')



## End(Not run)

mirt documentation built on Sept. 11, 2024, 7:14 p.m.