by Michael Blastland and David Spiegelhalter

A nonfiction book based on a person who doesn’t exist is an unusual sort of work. But that is The Norm Chronicles. “Norm” represents that dream of probability theorists, the absolutely average person slap in the middle of every distribution curve. Unfortunately, as the authors of The Norm Chronicles admit, such a person does not exist, and never will. None of us is exactly average, not even for the age we happen to be at any particular second.

So instead Professor David Spiegelhalter (professor for the public understanding of risk at Cambridge University) and Michael Blastland (deviser of BBC Radio 4’s excellent More or Less) extend their tale to three individuals: Norm, Kelvin — a laddish lout who takes every risk a man could — and Prudence, a pathologically cautious mother.

The point is meant to be that Kelvin and Prudence represent the extremes of response to risk: one person who believes danger is only a threat to others and one who when confronted with the information that there is a “million to one” risk of injury or illness by taking a certain course of action is convinced she will be “the one”.

Although this has satirical potential, the series of imaginary scenes involving these archetypes doesn’t quite come off. It is an admirable attempt to bring probability and statistics to life for a mass readership, but precisely because these are not real people it is impossible to feel interest in their lives, however wittily anatomised.

Fortunately, this mock-biographical thread is the least important thing in this book. What shines through is the authors’ informed determination to show how misleading some risk assessments are — and how the media skilfully enlarge such misapprehensions. For example, they look at a story on the front page of the Daily Express last year which declared “a daily fry-up boosts your cancer risk by 20%”. This striking headline is achieved by taking the five people out of 400 who typically suffer from this particular form of cancer during their lifetime and adding the fact that if every single one of the 400 sample ate an extra fry-up every day then the number of cancer sufferers would increase the toll from five to six. There’s your terrifying 20%. As the authors point out, the change in absolute risk is merely 0.25%: but that would hardly have made a front-page headline.

To be fair to those of us in the inky trade, scientists have become adept at phrasing their discoveries in ways which provoke the media’s hyperactive doom-mongering. The authors come up with the example of what happened when researchers discovered that a certain genetic variant present in 10% of the population protected them against high blood pressure: “Although published in a top scientific journal, the story received negligible press coverage until a knowing press officer rewrote the press release to say that a genetic variant had been discovered which increased the risk of high blood pressure in 90% of people.” Bingo!

Statistics can be dry as dust in their normal expression as mathematical variations from a mean — and you have to be an ace with numbers, like Spiegelhalter, to fathom the way probability can be assessed. Yet it can save vast numbers of lives — and expose those who are putting them (often unwittingly) at risk. Although the authors don’t mention this case, it was statistical comparative analysis of outcomes across the entire NHS that the Dr Foster website used to highlight to a disbelieving regulator the particular problems at the Mid Staffordshire NHS foundation trust — and which proved the complaints of individual families were of more than anecdotal significance.

What I hadn’t realised until reading The Norm Chronicles was that this concept of measuring outcomes across all hospitals and surgeries was introduced to British medical practice by Florence Nightingale; and that this was because she was “obsessed with statistics and a passionate admirer of Quetelet”. Adolphe Quetelet was the 19th-century Belgian statistician who invented the notion of “l’homme moyen” — the average man. That’s our Norm!

The question for all of us is this: can we deal with our own lives’ hazards by subjecting our actions to risk analysis of the sort so well outlined in this book? The authors are sceptical, although the Nobel prize-winning psychologist Daniel Kahneman has published wonderful work explaining how we could all “think like a statistician”. But in reality almost every one of us assesses risk like the simplest of all chance experiments — tossing a coin. Heads, I get cancer; tails, I don’t.

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