The GGUM package fits the generalized graded response model (GGUM; Roberts et al., 1996, 2000). It is based on marginal maximum likelihood (Roberts et al., 2000) to estimate the item parameters and an estimated a posteriori (EAP) method to estimate the person parameters.

This package produces comparable results to the ones based on the GGUM2004 program (Roberts et al., 2000; Roberts et al., 2006), for the GUM (Model 3 in GGUM2004) and the GGUM (Model 8 in GGUM2004). For those accustomed to using GGUM2004, this packages provides a useful set of functions that allow exporting data and code to GGUM2004, running GGUM2004, and retrieving the parameter estimates. Thus, if desired, one can run GGUM2004 and retrieve the results completely from within the R environment.