8

Categorical or Nominal Independent Variables

8.1 INTRODUCTION

8.1.1  Categories as a Set of Independent Variables

In this chapter, we introduce the options for treating categorical variables (nominal or qualitative scales) as independent variables in MRC. These IVs, such as religion or experimental treatments, may be represented by sets of IVs known as code variables. Each code variable represents a different aspect of the nominal variable. Taken together, the set of code variables represents the full information available in the original categories. As we will see, several different methods of selecting code variables are available, with the best method being determined by the researchers’ central questions.

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