This is a textbook in medical statistics for medical students, doctors, medical researchers, and others concerned with medical data. It will also be of interest to students of statistics who wish to learn about the practical applications of statistical methods. The fundamental concepts of study design and statistical inference are explained by illustration and example and, for those who wish to go further, the mathematical background is also described. The book is firmly grounded in medical research and the interpretation of the results of statistical calculations is emphasized. All the data in the many examples are real, from the author's own research and statistical consultation or from the medical literature, to which reference is made where possible. There are 75 multiple-choice questions, with annotated solutions, and 15 exercises in study design and data analysis, with fully explained solutions. The material covered includes the design of clinical trials and epidemiological studies, summarizing and presenting data, probability, standard errors, confidence intervals, significance tests, use of the t and Chi-squared distributions, regression and correlation, rank models, measurement error, reference ranges, mortality data, vital statistics, and the choice of statistical method. readership: medical students; doctors; medical researchers; teachers of statistics.