CDM (version 8.2-6)

sim_model: Simulate an Item Response Model

Description

Simulates an item response model given a fitted object or input of item response probabilities and skill class probabilities.

Usage

sim_model(object=NULL, irfprob=NULL, theta_index=NULL, prob.theta=NULL,
      data=NULL, N_sim=NULL )

Value

List containing elements

dat

Simulated item responses

theta

Simulated skill classes

theta_index

Corresponding indices to theta

Arguments

object

Fitted object for which the methods IRT.posterior, and IRT.data are defined.

irfprob

Array of item response function values (items \(\times\) categories \(\times\) skill classes)

theta_index

Skill class index for sampling

prob.theta

Skill class probabilities

data

Original dataset, only relevant for simulating item response pattern with missing values

N_sim

Number of subjects to be simulated

Examples

if (FALSE) {
#############################################################################
# EXAMPLE 1: GDINA model simulation
#############################################################################

data(sim.dina, package="CDM")
data(sim.qmatrix, package="CDM")
dat <- sim.dina
Q <- sim.qmatrix

# fit DINA model
mod <- CDM::gdina( dat, q.matrix=Q, rule="DINA")
summary(mod)

#** simulate new item responses (N equals observed sample size)
dat1 <- CDM::sim_model(mod)

#*** simulate item responses for N=2000 subjects
dat2 <- CDM::sim_model(mod, N_sim=2000)
str(dat2)

#*** simulate item responses based on input item response probabilities
#*** and theta_index
irfprob <- CDM::IRT.irfprob(mod)
prob.theta <- attr(irfprob, "prob.theta")
TP <- length(prob.theta)
theta_index <- sample(1:TP, size=1000, prob=prob.theta, replace=TRUE )
#-- simulate
dat3 <- CDM::sim_model(irfprob=irfprob, theta_index=theta_index)
str(dat3)
}