Providing a comprehensive picture of the design, conduct, analysis, and interpretation of non-experimental studies of both infectious and non-infectious diseases, the Second Edition of this widely used text has been thoroughly updated to take into account the numerous developments in epidemiology over the past decade. Since the first edition was published in 1986, additional sources of data have become available through the increasing use of computerized records for health-related purposes. Also, a better understanding of the uses and limitations of certain epidemiologic concepts has been...