[rkward-devel] item response theory plugin

[meik michalke]

hi,

i've been planning this for a long time, now i have finally started working on 
a plugin for data analysis unter the item response theory approach :-)

i've implemented parameter estimation for dichotomous data last night, to fit 
the rasch, two parameter logistic and birnbaum three parameter model. the 
plugin relies on the ltm package:
 o http://wiki.r-project.org/rwiki/doku.php?id=packages:cran:ltm
almost all options of the rasch(), ltm() and tpm() functions are available, 
only the "parscale" control of tpm() and the two factor model of ltm() are 
missing, as of now.

my future plans are to develop additional dialogs for goodness-of-fit tests 
and ltm specific plot options (e.g. test information curves). but of course 
any suggestions are wellcome :-)

here's the plugin:
 o http://reaktanz.de/stuff/R/irt_plugin-0.01.tar.bz2
and some screenshots:
 o http://reaktanz.de/stuff/R/scrsht3_01_data_model.png 
 o http://reaktanz.de/stuff/R/scrsht3_02_options.png 
 o http://reaktanz.de/stuff/R/scrsht3_03_advanced_control.png 
there's also a quick&dirty wizard, but i'm not sure if it's really useful...

since the plugin needs the ltm package, i've included a simple library(ltm) 
call in the preprocess function. is there a better way to make sure it's 
loaded, except doing it manually?


viele gruesse :: m.eik

-- 
dipl. psych. meik michalke
institut f"ur experimentelle psychologie
abt. f"ur diagnostik und differentielle psychologie
heinrich-heine-universit"at
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