Graphical Methods for Categorical Data

Statistical methods for categorical data, such as loglinear models and logistic regression, represent discrete analogs of the analysis of variance and regression methods for continuous response variables. However. while graphical display techniques are common adjuncts to analysis of variance and regression, methods for plotting contingency table data are not as widely used. This paper provides a brief introduction to graphical methods that are useful for understanding the pattern of association among categorical variables. These methods can be helpful both for data exploration and for communicating results to others. The methods described include association plots for two-way tables. mosaic displays for multi-way tables~ correspondence analysis and effect plots for logit models.