TAM (version 0.04-43)

tam.threshold: Calculation of Thurstonian Thresholds

Description

This function estimates Thurstonian thresholds for item category parameters of (generalized) partial credit models (see Details).

Usage

tam.threshold(tamobj)

Arguments

tamobj

Object of class tam

Value

• A data frame with Thurstonian thresholds. Rows correspond to items and columns to item steps.

Examples

##############################################
# Example 1: ordered data - Partial credit model
data( data.gpcm )

# Model 1: partial credit model
mod1 <- tam.mml( resp=data.gpcm ,control=list( maxiter=200) )
summary(mod1)
##   Item Parameters -A*Xsi
##        item   N     M AXsi_.Cat1 AXsi_.Cat2 AXsi_.Cat3 B.Cat1.Dim1 B.Cat2.Dim1 B.Cat3.Dim1
##   1 Comfort 392 0.880     -1.302      1.154      3.881           1           2           3
##   2    Work 392 1.278     -1.706     -0.847      0.833           1           2           3
##   3 Benefit 392 1.163     -1.233     -0.404      1.806           1           2           3

# Calculation of Thurstonian thresholds
tam.threshold(mod1)
##                Cat1      Cat2     Cat3
##   Comfort -1.325226 2.0717468 3.139801
##   Work    -1.777679 0.6459045 1.971222
##   Benefit -1.343536 0.7491760 2.403168