#*[[Koch's postulates]] were the first criteria developed for epidemiological relationships. Because they only work well for highly contagious bacteria and toxins, this method is largely out of favor.
#*[[Epidemiology#Bradford Hill criteria|Bradford-Hill Criteria]] are the current standards for epidemiological relationships. A relationship may fill all, some, or none of the criteria and still be true.
#Publish the results.<ref>{{cite book | last1 = Austin, | first1 = Donald F.,and| S.last2 B.= Werner | first2 = S. Benson | name-list-format = vanc | title = Epidemiology for the health sciences: a primer on epidemiologicalepidemiologic concepts and their uses.Springfield,| Ill:date C.= 1982 | publisher = Charles C. Thomas | ___location = Springfield, 1974Ill. Print.| isbn = 978-0-398-02949-4 | edition = 7th }}</ref>
== Measures ==
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==Limitations==
Epidemiological (and other observational) studies typically highlight ''associations'' between exposures and outcomes, rather than causation. While some consider this a limitation of observational research, epidemiological models of causation (e.g. Bradford Hill criteria)<ref>{{Citecite journal |last vauthors = Fedak|first=KristenM.|last2=KM, Bernal|first2=Autumn|last3= A, Capshaw|first3=ZacharyA.|last4=ZA, Gross S |first4=Sherilyn|date=2015-09-30| title = Applying the Bradford Hill criteria in the 21st century: how data integration has changed causal inference in molecular epidemiology |url=https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4589117/| journal = Emerging Themes in Epidemiology | volume = 12 | pages = 14 | date = 2015-09-30 | pmid = 26425136 | pmc = 4589117 | doi = 10.1186/s12982-015-0037-4|issn=1742-7622|pmc=PMC4589117|pmid=26425136 }}</ref> contend that an entire body of evidence is needed before determining if an association is truly causal.<ref>{{Citecite web | url = http://sphweb.bumc.bu.edu/otlt/MPH-Modules/EP/EP713_Causality/EP713_Causality_print.html | title = Causal Inference |website publisher =sphweb.bumc.bu.edu Boston University School of Public Health |access-date=2018-04-01}}</ref> 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.
