pcm.conversion {sirt} | R Documentation |
Conversion of the Parameterization of the Partial Credit Model
Description
Converts a parameterization of the partial credit model (see Details).
Usage
pcm.conversion(b)
Arguments
b |
Matrix of item-category-wise intercepts |
Details
Assume that the input matrix b
containing parameters
is defined according to the following parametrization of the partial credit
model
if item possesses
categories.
The transformed parameterization is defined as
The function pcm.conversion
has the and
parameters as values. The
parameter is simply
.
Value
List with the following entries
delta |
Vector of |
tau |
Matrix of |
Examples
## Not run:
#############################################################################
# EXAMPLE 1: Transformation PCM for data.mg
#############################################################################
library(CDM)
data(data.mg,package="CDM")
dat <- data.mg[ 1:1000, paste0("I",1:11) ]
#*** Model 1: estimate partial credit model in parameterization "PCM"
mod1a <- TAM::tam.mml( dat, irtmodel="PCM")
# use parameterization "PCM2"
mod1b <- TAM::tam.mml( dat, irtmodel="PCM2")
summary(mod1a)
summary(mod1b)
# convert parameterization of Model 1a into parameterization of Model 1b
b <- mod1a$item[, c("AXsi_.Cat1","AXsi_.Cat2","AXsi_.Cat3") ]
# compare results
pcm.conversion(b)
mod1b$xsi
## End(Not run)
[Package sirt version 4.1-15 Index]