irtoys-package {irtoys}R Documentation

Estimate and plot IRT models bor binary responses

Description

Provides a common interface to the estimation of item parameters in IRT models for binary responses with three different programs (ICL, BILOG, and ltm, and a variety of functions useful with IRT models.

Details

The irtoys package contains a bunch of functions potentially useful to those teaching or learning Item Response Theory (IRT). Although there is no shortage of good IRT programs, those tend to have wildly different and often unwieldy user interfaces. Besides, no single program does everything one needs. Item parameters can be estimated with a program like ICL or BILOG, non-parametric approaches are implemented in TestGraf, transformation to a common scale needs ST, and so on. Some programs, such as ICL, have no graphical capabilities at all, while others offer stunning interactive graphics but refuse to output a Postscript file. Package irtoys provides a common interface to some of the most basic functions in ICL, BILOG, and R's own ltm, some of the functionality of TestGraf and ST, and a variety of other functions. Those who want to take advantage of the full functionality of ICL, BILOG & Co. must still master their syntax.

To take full advantage of irtoys, one needs some IRT software. Package ltm is automatically loaded. ICL by Brad Hanson can be downloaded from his site, www.b-a-h.com. Executables are provided for Windows, Linux, and Macintosh. On Windows, place icl.exe in a directory that is included in the PATH variable (c:\windows and the R/bin directory are expected to always work). On Linux, place icl in the /usr/bin/ directory, and make it executable. For Macintosh, please ask somebody who really knows.

BILOG is commercial software sold by SSI — see www.ssicentral.com for further detail. On Windows, make sure that the three files BLM1.EXE, BLM2.EXE, and BLM3.EXE, for BILOG) are located in a directory that is included in the PATH variable (c:\windows and the R/bin directory are expected to always work). On Linux, place the three files in the /usr/bin/ directory, and make sure that wine is installed. For Macintosh, please ask somebody who really knows.

Author(s)

Ivailo Partchev <Ivailo.Partchev@uni-jena.de>

References

S. E. Embretson and S. P. Reise (2000), Item Response Theory for Psychologists, Lawrence Erlbaum Associates, Mahwah, NJ


[Package irtoys version 0.1.1 Index]