This self-contained account of the statistical basis of epidemiology has been written for those with a basic training in biology. It is specifically intended for students enrolled for a masters degree in epidemiology, clinical epidemiology, or biostatistics. No previous knowledge of the subject is assumed and mathematics is deliberately kept at a manageable level. The authors introduce the concept of likelihood at the outset, and develop the theory in a highly visual way, making use of a large number of diagrams. Based on a highly successful course, this book explains the essential statistics for all epidemiologists.