Fill in the Blanks Epidemiological Methods 1: Beginning QuestionsOnline version Beginning Questions by Ash Stivers 1 individual population Public health focuses on health while medicine focuses on health . 2 safety water risk vaccinations 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 population disease causes trends 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 frequency size disease Epidemiologists quantify the disease in a population by developing a definition of , mechanism for cases within specified populations , and determining population . 5 exposure disease 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 .