Dictionary Epidemiology Fifth edition Edited for the International Epidemiological Association Miquel Porta Professor of Preventive Medicine Public Health School of medicine, Universitat Autonoma de barcelona Senior Scientist, Institut Municipal d Investigacio Medica Bare Adjunct Professor of Epidemiology, School of Public Health University of North Carolina at Chapel Hill Sander greenland John M. Last OXFORD UNIVERSITY PRESSA Dictionary of Epidemiology of Fifth Edition Edited for the International Epidemiological Association by Miquel Porta Professor of Preventive Medicine & Public Health School of Medicine, Universitat Autònoma de Barcelona Senior Scientist, Institut Municipal d’Investigació Mèdica Barcelona, Spain Adjunct Professor of Epidemiology, School of Public Health University of North Carolina at Chapel Hill Associate Editors Sander Greenland John M. Last 1 2008