lordif (version 0.4.2)

probgpcm: calculates item response probabilities according to GPCM

Description

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

Usage

probgpcm(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 <[e-mail]>

Details

The Generalized Partial Credit Model (Muraki, 1992) is assumed.

References

Muraki, E. (1992). A generalized partial credit model: Application of an EM algorithm. Applied Psychological Measurement, 16, 159-176.

See Also

calcprob, probgrm

Examples

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