Regression models for unbalanced longitudinal ordinal data: computer software and a simulation study.
A computer program GGOREX in the form of a SAS macro is developed for the analysis of longitudinal ordinal data. It is extended from GEECAT and GEEGOR developed by Williamson, Lipsitz and Kim in their paper in 1999. An illustrative example with some preliminary data from a study conducted by the National Institute of Child Health and Human Development and the University of Alabama at Birmingham is given. Another set of computer programs is developed to make it possible to conduct a simulation study to validate the GGOREX procedure in a finite sample. A simple computer program in FORTRAN using the IMSL software library is developed to solve for the probability distribution of the longitudinal ordinal responses according to the correlation specification.