An Introduction to Categorical Data Analysis, Second Edition presents an introduction to the most important methods for analyzing categorical data. It summarizes methods that have long played a prominent role such as chi-squared tests and measures of association. It provides special emphasis, however, to logistic regression and loglinear modeling techniques for univariate and correlated multivariate categorical responses. This Second Edition presents new methods for clustered data, which are increasingly common in longitudinal studies, for example. Two new chapters discuss these methods along with improvements in major software. Chapter 10 deals with marginal models, including the generalized estimating equations (GEE) approach. Chapter 11 deals with random effects models through generalized linear models. Earlier chapters and appendices are updated.