probgrm {lordif}R Documentation

calculates item response probabilities

Description

Calculates a matrix of item response probabilities over a grid of theta values for an item

Usage

probgrm(theta, a, cb)

Arguments

theta a vector of theta values (e.g., quadrature points)
a a slope parameter value
cb a vector of category threshold values

Details

Graded Response Model (Samejima, 1969) is assumed.

Value

Returns a matrix of item response probabilities. The first dimension corresponds to the length of theta.

Author(s)

Seung W. Choi <s-choi@northwestern.edu>

References

Samejima, F. (1969). Estimation of latent ability using a response pattern of graded scores. Psychometrika Monograph, 17.

See Also

calcprob

Examples

##
probgrm(seq(-4,4,.1), 1.5, c(-1.2,0.5,1.5))

[Package lordif version 0.1-4 Index]