Example 1 — Check the axis before the shape
StandardProblem
A club posts this graph of its membership and calls it explosive growth. The vertical axis starts at 48 rather than 0. Say what the picture suggests, then what the numbers actually show.
Solution
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Read the first and last values: 50 members, then 54.
The numbers on the axis are the evidence. The steepness of the line is a drawing choice.
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Find where the vertical axis starts: 48, not 0.
Cutting the axis throws away the bottom of every point, so what is left is only the difference — drawn at full height.
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Compare the two: the line climbs most of the plot, while membership rose 4 out of 50, which is 8%.
The visual rise and the actual rise disagree, and that gap is the whole of the distortion.
Answer
The picture suggests membership shot up. It rose from 50 to 54, an increase of 8%. Drawn from 0, the same line would look almost flat.
Takeaway: Read the axis before the shape. A truncated axis exaggerates every change on it.