Saturday, May 14, 2016

The odds that odd things will happen

      David J. Hand. The Improbability Principle (2014) Say you go to Timmie’s and meet a person you haven’t seen for 50 years. “That’s a one in a million chance!” people say. Which means that in Canada it will happen to about 37 people. If you mean one in a million per year, that’s 37 this year, and about 1,500 or more during my lifetime. “One in a million” isn’t such overwhelming odds for or against after all.
     And that’s Hand’s point. We are bad at estimating odds. We react with Wows! to many things that we should expect to happen pretty often. Take the meeting a long-ago friend or neighbour: since we travel much more than we used to, the odds are far better than they used to be that we will come across people who know people we know, or that we knew some decades ago.
     Explaining why the improbable happens much more often than we expect, Hand provides an excellent introduction to probability and statistics. He writes clearly, with occasional glimmers of a pleasantly dry wit. Anyone who gambles should read this book. His discussion of drug testing will make the reader skeptical of pretty well all news about medical breakthroughs. Which reminds me that reporters of dramatic rate increases in something or other almost never give us the actual numbers. Reporting a 100% increase in some rare disease is much more exciting than reporting that 4 more deaths are expected this year in Toronto.
     And it’s much more thrilling to read about a traveller who changes his flight plans, and so isn’t one of the 300-odd who die when the plane crashes into a mountain. We don’t read about the thousands of people who have changed their flight plans every day, but have never missed being killed in a plane crash.
     Well done, recommended. ***½

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