Visual Design and Avoiding Misleading Charts

Why design matters

Design affects how quickly a reader understands a chart and whether they interpret it correctly.

Design checklist:

Scales and baselines

Example of distortion: Two bars of 98 and 102 on an axis starting at 95 look like a 5× difference. The real difference is about 4%.

Colour and accessibility

• Use colour consistently (e.g., the same colour for "North" in every chart).
• Highlight what matters: grey for context, one accent colour for the focus.
• Don't rely on colour alone. Add labels, patterns, or direct annotations.
• Use colour-blind-friendly palettes. Red–green combinations are the most common problem.
• Check that the chart still works in greyscale and with sufficient contrast.
• Use sequential palettes for ordered values, diverging palettes for values above or below a midpoint, and categorical palettes for groups.

Example

• A strong title states the finding, provided the analysis supports it.
• Add a subtitle or note explaining the period and metric definition.

Common mistakes

Try it: Review a chart you find online. Check its title, axes, scale, units, source, and whether the visual could lead a reader to a wrong conclusion.