Abstract
Epidemiology is the study of the causes and consequences of disease in human populations. The aim is to study a sample of a population to make assumptions about the state of health of a broader population, and then to apply these findings to the individual. To calculate an incidence or prevalence rate of a specific condition, the denominator or underlying population at risk needs to be specified over some time interval. The population needs to be defined in advance and enumerated and some standardized definitions employed. Common terminology allows studies to be linked and permits the broader study of national disease statistics that are used to define the health of our nation. Statistics regarding mortality, the incidence and prevalence of disease, and analyses of time trends require large efforts to collect the necessary data to make any meaningful statements. The US Census is the main source of most of our
