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.

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':
plot(x, xlab = "Person Raw Scores", ylab = "Person Parameters (Theta)", main = NULL, ...)

Arguments

object Object of class eRm.
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.

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.
npar Number of parameters.
niter Number of iterations.
thetapar Person parameter estimates.
se.theta Standard errors of the person parameters.

Note

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(raschdat1)
raschNA <- raschdat1
raschNA[1:40,1] <- NA                      #first item not presented
raschNA[41:100,2] <- NA                    #second item not presented
res <- RM(raschNA, se = FALSE)             #Rasch model without standard errors
pres <- person.parameter(res)
print(pres)                                #person parameteres round to 5 digits
summary(pres)


[Package eRm version 0.9.1.1 Index]