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According to this Hierarchy of Evidence, most
epidemiologic studies fall in the lower half. That’s because the research that Public
Health practitioners, as epidemiologists can conduct are usually observational in nature.
As such, these researchers do not have the control that would enable them to truly say
that “A causes B.” What they can say, however, is “A may cause B.” This is the
reason why epidemiologic studies need to have good research design that would allow
replication so that results from many studies can build up an “overwhelming” body of
evidence that the associations found can be considered causal associations. |