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Know Your Chances - Book Review

Layman's Guide to Understanding Health Statistics

Sep 22, 2009 Maija Haavisto

Medical statistics are everywhere, but they are often hard to understand and may seem confusing, contradicting or misleading. This textbook helps you solve the riddle.

There is a proverb about statistics being the biggest possible lie, which may be exaggerated, but it is certainly easy to mislead with them. Sometimes the misleading happens accidentally (such as when a busy reporter quickly glances over a press release when writing an article), but many companies also want to use statistics to further their own purposes.

Know Your Chances: Understanding Healthy Statistics (University of California Press, 2008, ISBN 978-0520252226) by Steven Woloshin, Lisa M. Schwartz and H. Gilbert Welch is a highly practical guide aimed at the laymen. It focuses on understanding the concept of risk and how it pertains not only to the population as a whole, but the reader in particular, thus helping them to make better informed choices.

The book explains the difference between absolute and relative risk reduction, but also how it is possible that a person's colon cancer risk can be both 1/19 and 5/10,000 (depending on the time frame used) - and how big the risk really is compared to the risk of dying from other causes.

Description

The book is very textbook-like. It is well written and the readability is improved by frequent information boxes, sidebars, charts, diagrams and illustrations. There are also quizzes to test whether the reader has understood the message. The book requires no previous knowledge about medicine or statistics, as everything is clearly explained.

The mathematic concepts d in the book are very simple and need not turn anyone away. The difficult part about simplified health statistics is not that they are difficult mathematically, but that they can be expressed in various different ways (and are usually incomplete) leading to different intepretations.

Even though there are many imaginary examples used in illustrating the message, all the numbers and health statistics in the book are real. This is enlightening, but can be somewhat unsettling for smokers, as the book relies heavily on statistics about causes of death at different ages - which are much larger for smokers.

The book is divided into four parts, which are further divided into chapters. The parts are

What is my risk
Can I reduce my risk
Does risk reduction have downsides
Developing healthy skepticism

There are also various appendices, such as a summary, glossary, index and additional resources (e.g. links to reliable sources of health statistics.

The different sides of risk are best defined at the end of Part 1:

Risk of what (death, illness, something else)
How big is the risk (out of how many, in what time frame)
Does the risk info reasonably apply to me
How does this compare with other risks

Overview

Know Your Chances: Understanding Healthy Statistics is intended to make one capable to intepret health news and information, but it does not contain any information about P values or other statistical devices utilized in actual medical articles. At 142 pages it is pretty short, which makes it a very quick read, but too simplistic for some readers.

Most doctors and researchers probably already understand statistics at the basic level presented in the book, but the book is recommended to all medical writers and journalists who ever write about health-related subjects. It would not hurt anyone to read the book and even older children would probably find it easy to understand.

What is special about the book is that the authors, all MDs, actually tested its "efficacy" in a randomized "placebo-controlled" trial, which showed that people were both more likely to pass and get an A in a test that measured their understanding of health risk than people who read a "placebo" book! Even better, no side effects were reported.

The copyright of the article Know Your Chances - Book Review in General Medicine is owned by Maija Haavisto. Permission to republish Know Your Chances - Book Review in print or online must be granted by the author in writing.

Know Your Chances: Understanding Health Statistics