Qualitative vs. Quantitative Variables: What’s the Difference?

In statistics, there are two types of variables:

1. Quantitative Variables: Sometimes referred to as “numeric” variables, these are variables that represent a measurable quantity. Examples include:

  • Number of students in a class
  • Number of square feet in a house
  • Population size of a city
  • Age of an individual
  • Height of an individual

2. Qualitative Variables: Sometimes referred to as “categorical” variables, these are variables that take on names or labels and can fit into categories. Examples include:

  • Eye color (e.g. “blue”, “green”, “brown”)
  • Gender (e.g. “male”, “female”)
  • Breed of dog (e.g. “lab”, “bulldog”, “poodle”)
  • Level of education (e.g. “high school”, “Associate’s degree”, “Bachelor’s degree”)
  • Marital status (e.g. “married”, “single”, “divorced”)

Quantitative vs. Qualitative variables

Every single variable you will ever encounter in statistics can be classified as either quantitative or qualitative.

Example: Classifying Quantitative & Qualitative Variables

Consider the following dataset with information about 10 different basketball players:

There are five total variables in this dataset. Two of them are qualitative variables and three of them are quantitative variables:

Qualitative vs. quantitative variables

Summarizing Quantitative & Qualitative Variables

We can use many different metrics to summarize quantitative variables, including:

However, we can only use frequency tables and relative frequency tables to summarize qualitative variables.

To illustrate this, let’s once again consider the dataset from the previous example:

Qualitative vs. quantitative variables

For the quantiative variable Seasons Played, we can calculate the following metrics:

  • Mean: 11.5
  • Median: 12
  • Mode: 12
  • Range: 8
  • Interquartile Range: 4.5
  • Standard Deviation: 2.915

These metrics give us a good idea of where the center value is located as well as how spread out the values are for this variable.

And for the qualitative variable Position, we can create a frequency table to describe how often different values occur:

This table lets us quickly see how frequently each position (G=guard, F=forward, C=center) occurred in the dataset.

Additional Resources

Descriptive vs. Inferential Statistics
Statistic vs. Parameter
Levels of Measurement: Nominal, Ordinal, Interval and Ratio

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