Supplementary material to the article

Dr C. Wheadon Predicted score distributions under Item Response Theory models

For the code to work correctly, the working directory in the R session must be changed (via the "setwd" function) to the base directory of the supplemental material (i.e., the directory that contains this README.txt file).

The R library inline must be installed and working correctly for the C++ to compile on the fly

The files in the bugs directory are taken from Curtis, S.M. (2010) BUGS Code for Item Response Theory, Journal of Statistical Software, Vol. 36, Code Snippet 1

Below is a description of each file in the supplementary material.

File Description

plot_gg Functions to produce the graphical displays with ggplot2 pfunctions.R Various probability functions functions.R Functions from Curtis, S.M. (2010) wl_cpp.R Inline C++ function for the Wingersky-Lord algorithm
wlord_rasch.R Rasch example wlord_pc.R Partial Credit Model example wlord_2pl.R 2 parameter IRT model wlord_2plt.R 2 parameter testlet model wlord_gpc.R Generalized Partial Credit Model wlord_3pl.R 3 parameter IRT model wlord_ppmc_pc.R Partial Credit Model with PPMC wlord_ppmc_gpc.R Generalized Partial Credit Model with PPMC wlord_pc_gpc.R GPCM compared to PCM wlord_4models.R Comparison of 4 dichotomous models with chi-square statistic