Qualitative Data

Qualitative data describe attributes or categories of a population and are also called categorical data.

Opening

A common mistake is to think that all data are numbers. But some of the most important data — hair color, blood type, the street you live on — are words, not numbers, and treating them as numbers would be meaningless.

The idea

Qualitative data describe attributes or categories of a population and are also called categorical data.

Two kinds of data

Data can come from a population or a sample, and most data fall into one of two broad categories: qualitative or quantitative. This unit focuses on qualitative data; quantitative data are covered in the Quantitative Data Types unit.

Vocabulary· 2 terms

Qualitative data are generally described by words or letters. For instance, hair color might be black, dark brown, light brown, blonde, gray, or red. Blood type might be AB+, O-, or B+. Researchers often prefer quantitative data because it lends itself more easily to mathematical analysis — it does not make sense to find an average hair color or blood type.

Easily confused

Looks like

Both are types of data, and sometimes a category like 'three books' looks like a number.

Actually

Qualitative data are words or letters describing attributes; quantitative data are always numbers from counting or measuring.

The distinction matters because you cannot do arithmetic on qualitative data — averaging hair color is meaningless.

Quantitative data

Quantitative data are always numbers and are the result of counting or measuring attributes. They may be discrete (from counting) or continuous (from measuring). These are defined in the Quantitative Data Types unit.

Vocabulary· 2 terms

Worked example

Classify each type of data from a supermarket trip.

1
Identify the soup data: the kinds of soup (tomato bisque, lentil, Italian wedding) are categories.
The kind of soup is an attribute described by words, not a number.
2
Identify the nut data: walnuts and peanuts are categories.
The type of nut is a category, not a measured amount.
3
Identify the vegetable data: broccoli, cauliflower, spinach, carrots are categories.
The kind of vegetable is an attribute, not a count or measurement.
4
Identify the dessert data: the two desserts are categories.
The kind of dessert is a category.

All the data in this example are qualitative (categorical) data.

Definition

quantitative continuous data

Data that are not only made up of counting numbers, but that may include fractions, decimals, or irrational numbers; often the results of measurements.

Data from measuring, like lengths, weights, or times.

Which of the following is an example of qualitative data?

Qualitative data are also called categorical data. The two terms are used interchangeably.

Recap

Say each point to yourself, then tap it to check.

They are also called categorical data.

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Source

Barbara Illowsky and Susan Dean

Licensed under CC BY 4.0. This course is an adaptation, not the original work.

Access for free at openstax.org/details/books/introductory-statistics-2e