MEPX
Chapter 7 of 13All chapters
  1. 1What analysis is for
  2. 2Types of data
  3. 3Collecting and sampling
  4. 4Cleaning data
  5. 5Describing the middle
  6. 6Describing the spread
  7. 7Choosing a chart
  8. 8Correlation
  9. 9Getting to causation
  10. 10Hypothesis testing
  11. 11Traps and paradoxes
  12. 12Tools of the trade
  13. 13Communicating results

Chapter 7 of 13

Choosing a chart

The picture is an argument.

Match chart to question

Bars compare values across categories. Lines show change over time. Scatter plots show the relationship between two numbers. Histograms show the shape of one.

  • Lengths from a shared baseline are the easiest thing for people to compare.
  • Pie charts ask people to compare angles, which they do badly. Use bars.

Honest axes

A truncated axis exaggerates a difference and a stretched one hides it. Start bar charts at zero, label units, and never use a second y-axis to imply a relationship.