While Epidemiology has long been associated with providing methods with which to conduct studies that can be used to aid in developing public health policy, the practice of Epidemiology actually includes the prudent use of available statistics.

Many measures are based on these available statistics. For example, measures based on vital statistics are used to indicate the magnitude of health problems. Because these statistics have been available for many years, and will continue to be in the future, they allow public health practitioners to evaluate the effectiveness of interventions by comparing the measures that use these statistics over time.