Population Reference Bureau Population Bulletin Vol. The ultimate purpose of epidemiology is the treatment and prevention of health problems that threaten the quality and length of people's lives. To design, target, and implement successful health interventions, scientists need to understand the etiology of specific health problems. This is the domain of analytic epidemiology.
Analytic studies test hypotheses about exposure to risk factors and a specific health outcome.
All the members of the study cohort are assumed to be free of that disease at the beginning of the study. The strength of the association between the exposure and a specific health outcome is measured by the rate ratio. The rate ratio indicates the likelihood that those exposed to asbestos would develop lung cancer relative to the likelihood that those not exposed would get lung cancer. Case-control is the second major type of analytic study. Researchers then reconstruct the exposure history of the two groups to determine which factors might explain why one group developed the disease.