rasch.prox {sirt}

PROX Estimation Method for the Rasch Model

Description

This function estimates the Rasch model using the PROX algorithm (cited in Wright & Stone, 1999).

Usage

rasch.prox(dat, dat.resp=1 - is.na(dat), freq=rep(1,nrow(dat)),
    conv=0.001, maxiter=30, progress=FALSE)

Arguments

dat

An N \times I data frame of dichotomous response data. NAs are not allowed and must be indicated by zero entries in the response indicator matrix dat.resp.

dat.resp

An N \times I indicator data frame of nonmissing item responses.

freq

A vector of frequencies (or weights) of all rows in data frame dat.

conv

Convergence criterion for item parameters

maxiter

Maximum number of iterations

progress

Display progress?

Value

A list with following entries

b

Estimated item difficulties

theta

Estimated person abilities

iter

Number of iterations

sigma.i

Item standard deviations

sigma.n

Person standard deviations

References

Wright, B., & Stone, W. (1999). Measurement Essentials. Wilmington: Wide Range.

Examples

#############################################################################
# EXAMPLE 1: PROX data.read
#############################################################################

data(data.read)
mod <- sirt::rasch.prox( data.read )
mod$b       # item difficulties