In epidemiology,<unk> es are used to understand the relationship between outcome and exposure at a population level, where 'population' represents a group of individuals with a shared characteristic such as geography, ethnicity, socio-economic status of employment. What differentiates<unk> es from other studies is that the unit analysis being studied is the group, therefore inferences cannot be made about individual study participants. On the other hand, details of outcome and exposure can be generalized to the population being studied. Examples of such studies include investigating associations between units of grouped data, such as electoral wards, regions, or even whole countries.
Ecological study
Natural history study
Retrospective cohort study
Population study
Cohort study
Prospective cohort study
Multiple baseline design
Randomized controlled trial