. Ecological descriptive studies: Ecological is relating to or concerned with the relation of living organisms to one another and to their physical surroundings.
- an ecological unit (a village, town or country)
* some of cross-sectional surveys, ecological studies , some hypothesis testing may be appropriate.
4.
Analytical studies
- The hallmark of an analytic epidemiologic study is the use of a valid comparison group.
- search for causes and effects, or the why and the how
- to test hypotheses about causal relationships
types of analytical designs
1) Cohort study