SUDAAN is a statistical software package for the analysis of correlated data, including but not limited to the analysis of correlated data encountered in complex sample surveys. Correlation between observations may exist, for example, in multi-stage studies where units such as geographic areas, schools, telephone area codes, or hospitals are sampled at the first stage of selection. A correlation may exist between observations due to the increased similarity of the observations located in the same cluster compared to observations between clusters. During any statistical analysis with survey data, the complex design features of the study, including clustering, unequal weighting, stratification, and selection with or without replacement, should be accounted for during the analysis. Standard software packages that do not account for the complex design features ...