Variable Types

When interpreting data and using data displays, it is essential to understand the types of variables involved. All variables come in one of two forms: quantitative or categorical. A quantitative variable is a variable that can be measured as a number. Some examples are height, age, crop yield, GPA, salary, and temperature. Any variable that is not quantitative is categorical. Categorical variables are variables with no natural sense of ordering. Some examples are hair color, gender, field of study, college attended, and political affiliation. Each of these examples has no numerical value.

Data is more easily manipulated in an analysis spreadsheet when it's coded quantitatively; categorical variables are often disguised as quantitative variables. For example, one might record gender information coded as 0 = Male, 1 = Female. However, the variable is still categorical; it is not naturally measured as a number.