13 Generalized linear models

This chapter covers

  • Formulating a generalized linear model
  • Predicting categorical outcomes
  • Modeling count data

In chapters 8 (regression) and 9 (ANOVA), we explored linear models that can be used to predict a normally distributed response variable from a set of continuous and/or categorical predictor variables. But in many situations, it’s unreasonable to assume that the dependent variable is normally distributed (or even continuous). For example:

  • The outcome variable may be categorical. Binary variables (for example, yes/no, passed/failed, lived/died) and polytomous variables (for example, poor/good/excellent, Republican/Democrat/independent) clearly aren’t normally distributed.

  • The outcome variable may be ...

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