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lordif (version 0.3-3)

probgrm: calculates item response probabilities according to GRM

Description

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

Usage

probgrm(theta, a, cb)

Value

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

Arguments

theta

a vector of theta values (e.g., quadrature points)

a

a slope parameter value

cb

a vector of category threshold values

Author

Seung W. Choi <choi.phd@gmail.com>

Details

The 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, probgpcm

Examples

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

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