I have always thought of myself as something of an outsider and troublemaker, so it is with some humility that I prepare the sixth edition of this book, 24 years after the first edition appeared. Then, as now, the book had an unusual perspective: that many papers in the medical literature contained avoidable errors. At the time, the publisher, McGraw-Hill, expressed concern that this “confrontational approach” would put off readers and hurt sales. They also worried that the book was not organized like a traditional statistics text.

 

Time has shown that the biomedical community was ready for such an approach, and the book has achieved remarkable success. Over time, it has evolved to include more topics, including power and sample size, more on multiple comparison procedures, relative risks and odds ratios, and survival analysis. Rather than adding more statistical tests in this edition, I have expanded the discussion of the qualitative issues in the use of statistics, such as what a random sample is, why it is important, the differences between experimental and observational studies, and bias and how to avoid it. I also completely rewrote the presentation of power in a continuing effort to make this daunting subject intuitive. This edition also continues the process of updating the examples and problems to use more contemporary material. At the same time, many of the original examples from the first edition remain; they have worked well over time and nothing seemed to be gained in messing with success just to change things.

 

By far, the biggest change in this sixth edition is a complete redesign of the illustrations in the book to use color. I wanted to use color in this book from the beginning because I thought that color would make it easier to communicate the important intuitive ideas of populations, sampling, randomness, and sampling distributions that underlie applied biostatistics. The addition of color is more than cosmetic; it substantially improves the presentation of ideas in the book.

 

This book has its origins in 1973, when I was a postdoctoral fellow. Many friends and colleagues came to me for advice and explanations about biostatistics. Since most of them had less knowledge of statistics than I did, I tried to learn what I needed to help them. The need to develop quick and intuitive, yet correct, explanations of the various tests and procedures slowly evolved into a set of stock explanations and a 2-hour (color) slide show on common statistical errors in the biomedical literature and how to cope with them. The success of this slide show led many people to suggest that I expand it into an introductory book on biostatistics, which led to the first edition of Primer of Biostatistics in 1981.