lordif (version 0.1-4)

probgrm: 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

Value

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

Details

Graded Response Model (Samejima, 1969) is assumed.

References

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

See Also

calcprob

Examples

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