This highly successful guide, w in its fifth edition with sales in excess of 26,000, is essential reading for all those requiring a basic understanding of epidemiology-the study of how often and why diseases occur in different groups of people. Assuming prior kwledge of the subject, it guides the vice through both the theory and practical pitfalls with the aid of familiar examples. The subjects covered in this book include: What is Epidemiology?; Quantifiying Disease in Populations; Comparing Disease Rates; Measurement Error and Bias Planning and Conducting a Survey; Ecological Studies; Longitudinal Studies; Case-control and Cross Sectional Studies; Experimental Studies; Screening Outbreaks of Disease; and, Reading Epidemiolgical Reports. This concise and readable book, w revised and updated, is an invaluable tool for all health care professionals and medical students whether they are getting to grips with epidemiology for the first time or as a practical revision aid for those needing to refresh or update their kwledge.