Misleading charts

The same figures can tell different stories. Four common tricks:

1. The y-axis does not start at zero. The difference between 51 and 53 looks like a doubling.
2. Only part of the time is shown. One year pointing upwards, within a ten-year period pointing downwards.
3. The wrong chart type. A line chart over categories suggests a development that does not exist.
4. Areas instead of lengths. A circle with twice the radius looks four times as large.

And a fifth: pie charts where the parts do not add up to 100 %.

Examine a chart — four questions:

Question	Why
Where does the y-axis start?	it decides how large the difference looks
Which period is shown, and why that one?	the selection can reverse a trend
How many are included (n)?	3 out of 4 = 75 %, but it says almost nothing
Who made the chart, and what do they want?	the intention governs the choices

Try it: take the figures 51, 52, 53, 52 and draw them twice — once with the y-axis from 0 to 60, once from 50 to 54. The same data, an entirely different impression. Which is honest? The first — unless small differences are the point itself, and then it has to say so clearly.