More On Categorical Data Analysis
About the Second Edition
As the SAS System continued to grow in
features, the first edition, for all its merits, became incomplete. Two motivations were primary: the capacity for
generalized estimating equations (GEE) analysis in PROC GENMOD and the increasing number of exact methods that were
available for PROC FREQ and PROC NPAR1WAY. Work began in the spring of 1999, with the hope of a release with Version 8, but
as plans for 8.1 included some important techniques such as exact logistic regression, we decided to write the book based on
Release 8.1.
Major enhancements to the book include a fairly large chapter on GEE methods, including its applicability to longitudinal studies and crossover studies; its usefulness when missing data is encountered is illustrated with two examples. In addition, several data sets are analyzed in both the GEE chapter and the conditional logistic regression chapter (revamped), and the population-averaged and subject-specific approaches are compared. Two additional examples illustrate how the GEE method can be useful for univariate responses to handle overdispersion and fit the partial proportional odds model.