get_thresh {scaleAlign}

Get Thurstone thresholds

Description

Find Thurstone thresholds from a fitted model.

Usage

get_thresh(pars, itemtype, item_ind, alpha = 1)

Arguments

pars

Vector of estimated item parameters

itemtype

Item type: "1PL", "PCM", or "PCM2".

item_ind

Vector with one element for each parameter indicating which item each parameter is associated with.

alpha

Vector of item steepnesses, with one element for each item. Recycled if of length 1.

Value

Vector of Thurstone thresholds

Examples

if(require(TAM)){

set.seed(2524)

diff <- rnorm(10)

N <- 500

th <- rnorm(N)

probs <- 1 / (1 + exp(-outer(th, diff, "-")))

dat <- apply(probs, 2, function(p) as.numeric(p > runif(N)))

# fit the model

mod <- TAM::tam.mml(resp = dat, irtmodel = "1PL")

get_thresh(mod$xsi$xsi, itemtype = "1PL", item_ind = 1:10)

}