Fill in the Blanks Epidemiological Methods 1: Beginning QuestionsOnline version Beginning Questions by Ash Stivers 1 population individual Public health focuses on health while medicine focuses on health . 2 safety vaccinations risk water Public health achievements that have improved life expectancy in the US over the past century include : routine , improved , sanitation and clean , modification of disease factors , and tobacco campaigns . 3 trends population disease causes The main objectives of epidemiology are : study the natural course of , determine the extent in a , identify patterns and , identify , and evaluate effectiveness . 4 counting disease size frequency Epidemiologists quantify the disease in a population by developing a definition of , mechanism for cases within specified populations , and determining population . 5 disease exposure population The many subspecialties of modern epidemiology are typically defined by , , or . 6 course molecular social Modern epidemiological research has expanded in these three directions : , , and life .