probgpcm function

calculates item response probabilities according to GPCM

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

probgpcm(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

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

Returns

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

References

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

Author(s)

Seung W. Choi choi.phd@gmail.com

See Also

calcprob, probgrm

Examples

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