How to Classify a Variable as Quantitative or Qualitative
In introductory statistics, it’s easy to get confused when classifying a variable or object as quantitative or qualitative. Quantitative means it can be counted, like “number of people per square mile.” Qualitative means it is a description, like “brown dog fur.” How to classify those variables:
Step 1: Think of a category for the items, like “car models” or “types of potato” or “feather colors” or “numbers” or “number of widgets sold.” The name of the category is not important.
Step 2: Rank or order the items in your category. Some examples of items that can be ordered are: number of computers sold in a month, students’ GPAs or bank account balances. Anything with numbers or amounts can be ranked or ordered. If you find it impossible to rank or order your item, you have a qualitative item. Examples of qualitative items are “car models,” “types of potato,” “Shakespeare quotes.”
Step 3: Make sure you haven’t added information. For example, you could rank car models by popularity or expense, but popularity and expense are separate variables from “car model.” If the item is “potatoes,” it’s qualitative. If the item is “number of potatoes sold,” it’s quantitative.