THE MATH OF LIFE AND DEATH

A welcome addition to the math-for-people-who-hate-math genre.

In his first book, Yates, the co-director of the Centre for Mathematical Biology at the University of Bath, cheerfully promises to arm readers “with simple mathematical rules and tools that can help you in your everyday life: from getting the best seat on the train, to keeping your head when you get an unexpected test result from the doctor….We will also…observe math in action as we highlight the steps we can take to help halt the spread of a deadly disease.” Evolution primed organisms to avoid danger; calculating has no survival advantage, so humans lack a talent for it, a deficit the author finds irresistible. Yates also looks at the mammogram anecdote, which serves as proof that even smart people mess up: A woman has a positive mammogram. If mammograms are 90% accurate and 1% of women have undetected breast cancer, what are the odds that this is bad news? Given a choice, many doctors will say 80% when the answer is about 9. They forget that 10% of the 99 healthy women will also test positive. Yates also points out the common mathematical errors that occur in the court system, where many fall for the “prosecutor’s fallacy.” For example, an accused person wears the identical shoe size as the criminal. Since only 4% of the population wears that size, the prosecutor claims that there is a 96% chance that he is guilty. Along with useful tips and intriguing examinations of a wide variety of algorithms (useful and useless), Yates loves delivering curious facts, in the vein of Freakonomics, and readers will be thankful. For example, almost every human possesses more than the average number of legs. Amputees lower the average, and no one has three.

All but the stubbornly innumerate will enjoy this amusing mathematical miscellany.