<unk>  (and other observational) studies typically highlight associations between exposures and outcomes, rather than causation. While some consider this a limitation of observational research,<unk>  models of causation (e.g. Bradford Hill criteria) contend that an entire body of evidence is needed before determining if an association is truly causal. Moreover, many research questions are impossible to study in experimental settings, due to concerns around ethics and study validity. For example, the link between cigarette smoke and lung cancer was uncovered largely through observational research; however research ethics would certainly prohibit conducting a randomized trial of cigarette smoking once it had already been identified as a potential health threat.
Epidemiological method
Epidemiology in Country Practice
Real world data
Diagnosis-related group
Comparison of birth control methods
Phases of clinical research
Patient-reported outcome
Clinical endpoint