Data Types

We often begin exploratory data analysis by examining the types of data that occur in a table. Although there are multiple ways of categorizing data types, in this book we discuss three broad types of data:

1. Nominal data, which represents categories that do not have a natural ordering. For example: political party affiliation (Democrat, Republican, Other), sex (male, female, other), and computer operating system (Windows, MacOS, Linux).
2. Ordinal data, which represents ordered categories. For example: T-shirt sizes (small, medium, large), Likert-scale responses (disagree, neutral, agree), and level of education (high school, college, graduate school). Ordinal and nominal data are considered subtypes of categorical data.
3. Numerical data, which represents amounts or quantities. For example: heights, prices, and distances.

We refer to these types as statistical data types, or simply data types.