Charts that inform.
WHAT A CHART IS FOR
Showing a pattern faster than a table would.
WHEN NOT TO USE ONE
When there are few numbers.
WHAT TO USE INSTEAD
A sentence, or a small table.
WHAT CHART SUITS WHAT
- Trends over time: lines
- Comparison of categories: bars
- Composition: use sparingly, and prefer bars
- Relationship between two measures: points
WHAT TO AVOID
Three-dimensional effects Pie charts with many segments Dual axes, which mislead
WHY DUAL AXES MISLEAD
The relationship shown depends on arbitrary scaling.
WHAT TO LABEL
Both axes, with units The chart, with what it shows
WHAT TO PUT IN THE TITLE
The conclusion, where there is one.
WHAT EXAMPLE SHOWS IT
Support volume fell after the documentation change, rather than Monthly support volume.
WHY
It tells the reader what to see.
WHAT TO REMOVE
Gridlines that are not needed Legends where direct labels work Anything decorative
WHAT TO CHECK
Whether the chart is readable when printed in one colour.
WHY
It frequently is.
WHAT TO STATE BENEATH
The source and the period.
WHAT TO TEST
Whether someone draws the intended conclusion unaided.
WHAT TO DO IF THEY DO NOT
Change the chart, not the audience.
