Statistics Tip of the Week: the values of a Categorical Variable are names of categories.

Categorical Variables are used in ANOMA, ANOVA, with Proportions, and in the Chi-Square Tests for Independence and Goodness of Fit. Categorical Variables are also known as "Nominal" (named) Variables and "Attributes" Variables.

​The concept can be confusing, because the values of a Categorical Variable are not numbers, but names of categories. The numbers associated with Categorical Variables come from counts of the data values within a named category.  Here's how it works:

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• In this example there are two Categorical Variables,  "Gender" and "Ice Cream (flavor)". 
• The values of the two Categorical Variables are the names of the categories for the Variable.  For example, the Categorical Variable "Gender" has 2 possible values: "female" and "male". 
• If we're going to use these Variables in a Chi-Square Test for Independence, for example, we need to have some numbers. The numbers are the counts of the data values in each category.  For example, the count of persons whose gender is "female" and whose favorite ice cream flavor is "vanilla" is 25.