Author: Gerd Gigerenzer
Uncertainty and risks pervade all facets of life, and they are central themes in healthcare. This book demonstrates the widespread problem of risk estimation, and suggests remedies to redress this. It demonstrates how to draw conclusions from numbers, and how to communicate risk (page 7). The author elucidates several risk-related concepts such frequencies, percentages, pre-test probabilities, absolute and relative risks, and reference class. He illustrates these with striking healthcare-related anecdotes such as HIV testing, mammography breast cancer screening, and prostate specific antigen (PSA) screening for prostate cancer.
The author addresses the major obstacles to the understanding of risk. One important hindrance is what he calls statistical innumeracy, ‘the inability to reason about uncertainties and risk’ (page 24). He also discussed the ‘illusion of certainty’ which distorts the perception of risk; he says ‘illusory certainty is part of our perceptual, emotional and cultural inheritance’ (page 14). The author refers to the ‘anatomy of the medical mind‘ which makes physicians, especially older ones, struggle to understand risks (page 107). Physicians also have difficulty with ‘drawing diagnostic inferences from statistics’; this is one explanation for ‘the reluctance in medicine to rely on evidence’ (page 90).
The book offers solutions to most of these problems by providing ‘tools for overcoming innumeracy that are easy to learn, apply, and remember’ (page 37). The author explains how to convert uncertainties to concrete risks, and he propounds simple laws such as ‘when thinking and talking about risks, use frequencies rather than probabilities’ (page 7). He cautions against using relative risk reduction to communicate benefits of interventions, preferring numbers needed to treat (NNT) and absolute risk reduction (page 36).
A major part of the book deals with the misconceptions around the benefits and risks of healthcare screening. The author discusses how screening influences the incidence of, and mortality from, cancer (page 57). He points out how screening detects many lesions that may never lead to clinical disease, but their detection leads to unnecessary tests and interventions (page 80). The book also explores the subject of informed consent in the context of HIV screening and pre-test counselling. He discusses, with illustrative examples, the positive predictive value (the probability of infection when a test is positive) and the sensitivity of tests (the likelihood that an infected person will test positive; page 132).
The author explores the wide-ranging implications of statistical innumeracy on society. He shows the legal implications of poor statistical thinking on judicial outcomes using examples such as wife battery, child abduction, and disputed paternity (page 159). He also shows how statistical ignorance may be used to manipulate society. He however says ‘… peoples difficulties in thinking about numbers need not be accepted’. He advocates the teaching of ‘clear thinking‘ and, proposing an approach based on the principles of his book, he reassures that ‘…with the aid of intuitively understandable representations, statistical thinking can become a habit of mind’ (page 245).
The author talking risk at a TED talk
This book addresses concepts that are difficult to appreciate, but are pivotal to healthcare. The author elucidates the issues around risk and uncertainty with relevant examples. The writing style is clear and the message is unambiguously simple. The author’s passion about the topic infuses every chapter. The difficulty with statistics is however deeply ingrained and the solutions are probably more complex than the author suggests. The book however clears the mystery behind the numbers and figures that permeate research papers and determine health policies. The tools in this book allows the doctor to question evidence intelligently, and to challenge reported benefits of interventions. I was particularly impressed by the discussion of health screening, and the often exaggerated claims made of its benefit.
This book addresses a subject which is fundamental to healthcare. Flawed statistical thinking has significant consequences and the author has done an excellent job of highlighting these. The book goes further to offer solutions to the problems and I recommend it to doctors.
- Publisher, place, date: Penguin Books, London, 2002
- Edition: 1st
- Number of chapters: 14
- Pages: 310
- Price: £9.98
- Star rating: 5 stars
- Other relevant books: Gut Feelings, Simple Heuristics that Make Us Smart