person.parameter {eRm}R Documentation

Estimation of Person Parameters

Description

Maximum likelihood estimation of the person parameters with spline interpolation for non-observed and 0/full responses. Extraction of information criteria such as AIC, BIC, and cAIC based on unconditional log-likelihood.

Usage

## S3 method for class 'eRm':
person.parameter(object)
## S3 method for class 'ppar':
summary(object, ...)
## S3 method for class 'ppar':
print(x, ...)
## S3 method for class 'ppar':
summary(object, ...)
## S3 method for class 'ppar':
plot(x, xlab = "Person Raw Scores", ylab = "Person Parameters (Theta)", main = NULL, ...)
## S3 method for class 'ppar':
logLik(object, ...)
## S3 method for class 'ppar':
IC(object)
## S3 method for class 'ppar':
confint(object, parm, level = 0.95, ...)

Arguments

object Object of class eRm in person.parameter and object of class ppar in IC.
x Object of class ppar.
xlab Label of the x-axis.
ylab Label of the y-axis.
main Title of the plot.
... Further arguments to be passed to or from other methods. They are ignored in this function.
parm Parameter specification (ignored).
level Alpha-level.

Details

If the data set contains missing values, person parameters are estimated for each missing value subgroup.

Value

The function person.parameter returns an object of class ppar containing:

loglik Log-likelihood of the collapsed data (for faster estimation persons with the same raw score are collapsed).
npar Number of parameters.
niter Number of iterations.
thetapar Person parameter estimates.
se.theta Standard errors of the person parameters.
hessian Hessian matrix.
j.loglik Unconditional (joint) log-likelihood value.
AIC AIC criterion.
BIC BIC criterion.
cAIC Consistent AIC criterion.

Author(s)

Patrick Mair, Reinhold Hatzinger

References

Fischer, G. H., and Molenaar, I. (1995). Rasch Models - Foundations, Recent Developements, and Applications. Springer.

Mair, P., and Hatzinger, R. (2007). Extended Rasch modeling: The eRm package for the application of IRT models in R. Journal of Statistical Software, 20(9), 1-20.

Mair, P., and Hatzinger, R. (2007). CML based estimation of extended Rasch models with the eRm package in R. Psychology Science, 49, 26-43.

See Also

itemfit.ppar,personfit.ppar

Examples


#Person parameter estimation of a rating scale model
data(rsmdat)
res <- RSM(rsmdat)
pres <- person.parameter(res)
print(pres)
summary(pres)
plot(pres)

#Person parameter estimation for a Rasch model with missing values
data(raschdat2)
res <- RM(raschdat2, se = FALSE)           #Rasch model without standard errors
pres <- person.parameter(res)
print(pres)                                #person parameters
summary(pres)
logLik(pres)                               #conditional log-lik value

#Extraction of IC's
IC(pres)


[Package eRm version 0.9-5 Index]