← Thinking Clearly

Chapter 4

Reading graphs and statistics

A chart can mislead without a single false number. An axis that doesn't start at zero makes small gaps look huge, a log scale tames fast growth, and a well-chosen start date can make almost any trend appear. This chapter teaches the questions to ask of any graph or statistic: where the scale starts, what the absolute numbers are, how big the margin of error is, who was asked, and whether two things moving together really have anything to do with each other.

11 cards

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  1. A bar chart whose axis doesn't start at zeroA truncated axis
  2. Axis where each step multiplies by 10Log scale
  3. Choosing only the dates that tell your storyCherry-picking
  4. "Doubles the risk", with no starting numberRelative risk
  5. The ±3% that comes with a pollMargin of error
  6. A poll that only asks people online at noonSelection bias
  7. From 10% to 12% is a rise of 2…Percentage points
  8. A pie chart's slices should add up to100%
  9. One value far from all the othersAn outlier
  10. Cheese eaten tracks deaths by bedsheet tanglingSpurious correlation
  11. Comparing countries fairly by dividing by populationPer capita