Types of Data

Key idea

Categorical vs numerical, discrete vs continuous.

In depth

Data are either categorical (labels such as colour, with nominal or ordinal order) or numerical (counts that are discrete, measurements that are continuous). The type decides which graphs and statistics make sense: you cannot average eye colours.

Worked example

Shoe size is discrete numerical, height is continuous, favourite subject is nominal, and a star rating is ordinal.

Real-world uses

• Deciding whether a survey answer is a category (colour) or a number (age) before analysing it

Common mistake

Treating numbers used as labels (such as phone numbers) as quantities.

How to learn this

1. Read the key idea and say it in your own words.
2. Work through the worked example, then try a similar problem.
3. Use the interactive lesson’s visual and mini-quiz to check the pattern.

Frequently asked questions

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Related beginner topics in Probability & Statistics

• Frequency Tables – Count how often each value occurs.
• Tally Charts and Pictographs – Simple visual summaries of counts.
• Bar Graphs – Compare categories using bars.
• Pie Charts – Show parts of a whole as sectors.
• Line Graphs – Show change over time.
• Mode – The most frequent value.