probgrm function

calculates item response probabilities according to GRM

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

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

The Graded Response Model (Samejima, 1969) is assumed.

Returns

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

References

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

Author(s)

Seung W. Choi choi.phd@gmail.com

See Also

calcprob, probgpcm

Examples

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