Cohort Study - gold standard when exploring the association between a risk factor or participation in a health program, and health status outcomes or health events.

Case-Control Study - more commonly used, less expensive, when outcome of interest is rare, and a random sample from a population would yield too few cases. Involves a retrospective assessment of differential exposure between 2 comparison groups.

Data from Entire Population - considered cross-sectional since collection or sampling of the exposure and outcome info is at the same point in time. Considered prevalence data. A relationship between exposure and outcome is the ratio of 2 prevalence rates, or relative prevalences.

Ecologic Designs - Data for exposure and disease are used in aggregated form and cannot be linked at the individual level.