The one-sentence summary

Treat information with great suspicion until you know the real story.


  • Seeing a pattern of stripes in the leaves, we would run from what looks like a tiger. There are illusions in numbers too, often just as intimidating. The book reveals what the numbers really show, and exposes the tiger that isn’t.
  • Life comes in numbers: public spending, health risks, who is rich and poor, the best and worst schools. The trick to seeing through them is to apply the lessons of your own experience, and investigate them more thoroughly.


The book works through most of the manners in which numbers will be presented, and shows how to make sense of them, using lots of examples from everyday news stories. Specifically relevant to business are:

  • Counting: counting things is very difficult, and the results often wrong
  • Chance: frequently things are truly random, but we still look for patterns
  • Up and down: numbers go one way or the other, regardless of what you do
  • Averages: disguise huge variation and squeeze everything into a mass
  • Targets: what they do not measure is as important as what they do
  • Risk: all that matters is what it means to you
  • Sampling: if the sample is flawed, so is the conclusion
  • Data: they are often plain wrong, so be careful drawing conclusions
  • Shock figures: are more likely wrong or misinterpreted than shocking
  • Comparison: mind the gap – they might not be comparable
  • Correlation: is not the same as causation – there may be no link

Everyone should read this book as a sanity check on the numbers we have thrown at us or bandy around ourselves – particularly politicians and journalists.


  • Not much. We all have to deal with numbers, but if you don’t understand them then don’t misrepresent them.