SUDAAN

SUDAAN is software for the statistical analysis of correlated data. It is specifically designed for analysis of cluster-correlated data from studies involving recurrent events, longitudinal data, repeated measures, multivariate outcomes, multi-stage sample designs, stratified designs, unequally weighted data, and without-replacement samples. SUDAAN fits marginal or population-averaged models using generalized estimating equations (GEE). Robust variance estimates are computed that fully account for intracluster correlation, unequal weighting, stratification, and without-replacement sampling.  You can use SPSS or SAS to manage your database and easily use SUDAAN to analyze your SPSS or SAS data sets.