branches of epidemiology
methods
Descriptive and analytic studies are the two main types of research design used in epidemiology for describing the distribution of disease incidence and prevalence, for studying exposure-disease association, and for identifying disease prevention strategies. Generally speaking, descriptive studies deal with the “what” questions, for example, describing “what happened” in terms of disease occurrence, while analytic studies ask the “why” questions, for example, why some people develop disease and others don't. [Source: Encyclopedia of Epidemiology; Descriptive and Analytic Epidemiology]
descriptive and analytic epidemiology