Reading graphs critically

Ages 13 to 17 Read alone · about 45 minutes

Read together

Graphs make data easy to see, and they can also mislead. In 1954, Darrell Huff wrote a famous book called “How to Lie with Statistics”. It showed how numbers and charts can give a false impression.

Common tricks include starting a bar chart's axis above zero, so small differences look huge. Another is picking only the time period that fits a story. A third is showing one average that hides how spread out the data is.

Another trap is confusing correlation with cause. Two things can rise together without one causing the other, for example ice cream sales and swimming accidents both rise in summer.

Do it

1. Find three graphs in news articles or reports. For each, check the axes, the scale, the source and the time period.
2. Draw a bar chart of the same data twice: once with the axis starting at zero, and once starting higher. Compare how it looks.
3. Find an example of correlation that is not cause. Explain a possible hidden third factor.
4. Make an honest graph of something in your life, such as the hours you slept each night this week, with clear labels and a source.

Talk about it

• What is this graph not showing?
• How could the same data tell a different story?

For the grown-up

Data literacy is an essential skill for citizens. Edward Tufte's work on data display also shows how to make graphs clear and honest. Practise checking claims together, using reliable sources.

Mark as done

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Where this comes from

• Darrell Huff, How to Lie with Statistics (W. W. Norton, 1954)
• Edward R. Tufte, The Visual Display of Quantitative Information, 2nd ed. (Graphics Press, 2001)

Written with AI assistance and checked against the sources listed. Please read it before sharing it with a child.