eRm (version 1.0-1)

sim.rasch: Simulation of Rasch homogeneous data

Description

This utility function returns a 0-1 matrix which fits the Rasch model.

Usage

sim.rasch(persons, items, seed = NULL, cutpoint = "randomized")

Arguments

persons

Either a vector of person parameters or an integer indicating the number of persons (see details)

items

Either a vector of item parameters or an integer indicating the number of items (see details)

seed

A seed for the random number generated can be set.

cutpoint

Either "randomized" for a randomized tranformation of the model probability matrix into the model 0-1 matrix or an integer value between 0 and 1 (see details)

Details

If persons or items is an integer value, the corresponding parameter vector is drawn from N(0,1). The cutpoint argument refers to the transformation of the theoretical probabilities into a 0-1 data matrix. A randomized assingment implies that for each cell an additional random number is drawn. If the model probability is larger than this value, the person gets 1 on this particular item, if smaller, 0 is assigned. Alternatively, a numeric probability cutpoint can be assigned and the 0-1 scoring is carried out according to the same rule.

References

Su\'arez-Falc\'on, J. C., & Glas, C. A. W. (2003). Evaluation of global testing procedures for item fit to the Rasch model. British Journal of Mathematical and Statistical Society, 56, 127-143.

See Also

sim.xdim, sim.locdep, sim.2pl

Examples

# NOT RUN {
#simulating Rasch homogenous data
#100 persons, 10 items, parameter drawn from N(0,1)
X <- sim.rasch(100, 10)

#person parameters drawn from uniform distribution, fixed cutpoint
ppar <- runif(100,-2,2)
X <- sim.rasch(ppar, 10, cutpoint = 0.5)
# }