Evidence Tier
human_observational
Last updated
Rung 2 on this site's ladder. A study of humans in which the investigator did not assign who was exposed, but some comparison exists, either between groups or against a documented baseline measured before exposure. It requires a defined population with stated inclusion criteria, reported follow-up and loss to follow-up, and named confounders whether or not they were adjusted for. The full criteria are at /evidence/rubric.
Flagged for specialist review
This entry describes something contested, or asserts a detail we have not been able to confirm against a settled source. It is published rather than withheld, with the flag visible, because an entry you can weigh beats a gap you cannot see.
Why it matters here
Every rung 2 claim on the site is worded to survive the possibility that the association is entirely confounded, which is why you will not see improves, reduces or causes attached to one.
What it is not
Association is not effect, and no sample size converts an observation into an assignment: a very large cohort is still rung 2. Self-reported use of grey-market material does not qualify, because nothing verifies that the substance matched the label, and a seller's survey of its own customers never qualifies at any size.
Also called
- observational
- cohort study
- cross-sectional
- registry data
- human observational
Cohort study, cross-sectional and registry data are different observational designs that all land on this one rung; the record names which design it was, because that affects how strongly it should be read.
Compounds carrying this term
None on file yet. This term is in the controlled vocabulary but no compound record currently uses it — which is a statement about our coverage, not about the term.