mirt (version 1.27.1)

testinfo: 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 estimated mirt object

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

a number signifying which group the item should be extracted from (applies to 'MultipleGroupClass' objects only)

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

References

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

Examples

# NOT RUN {
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')


# }