The most important concept in statistics is the probability model. Only by fully understanding this model can one fully understand statistical analysis. Utilizing models in epidemiology, the authors of this self-contained account have chosen to emphasize the role of likelihood. This approach to statistics is both simple and intuitively satisfying. More complex problems can be tackled by natural extensions of the simple methods. This exploration of the statistical basis of epidemiology has been written specifically for professionals and graduate students in epidemiology, clinical epidemiology, or biostatistics. The simple prerequisite--basic training in biology--assumes no previous knowledge and the mathematics is deliberately kept at a manageable level. Based on a highly successful course by two internationally known authors, this book explains the essentials of statistics for all epidemiologists.