Probability

The Italian actuary Bruno de Finetti, writing in 1931, was explicit: ‘Probability does not exist.’ Probability, it’s true, is simply the measure of an observer’s uncertainty; and in The Art of Uncertainty, the British statistician David Spiegelhalter explains how this extraordinary and much-derided science has evolved to the point where it is even able to say useful things about why matters have turned out the way they have, based purely on present evidence. Spiegelhalter was a member of the Statistical Expert Group of the 2018 UK Infected Blood Inquiry, and you know his book’s a winner the moment he tells you that between 650 and 3,320 people nationwide died from

Here’s a profound question about beards: is the number of acrobats with beards the same as the number of bearded people who are acrobats? Go with your gut instinct. It’s not a trick question. If you answer ‘yes’, then you’ve understood the central idea behind Bayes’s theorem. If you’re one of those people who likes to titter about how bad you are at mathematics, stop it. Retake your GCSE, learn how to pin this obviousness down in symbols, and you can produce artificial intelligence, forecast stock market collapses and understand this: P(A|B) = (P(B|A)∙P(A))/(P(B)) This is Bayes’s equation, the formula which, as Tom Chivers insists in this remarkable, bold book,