Evidence index
How we know it.
A subject tells you what a page is about. A method tells you what kind of evidence stands behind it, and how far that evidence reaches. The same handful of methods recur no matter what the question is about.
Measured by instrument
A number produced by a device placed in the environment — a pressure sensor, a sonar beam, a calibrated camera. The instrument, and its stated error, is the evidence.
4 answersInferred from a proxy
The quantity itself was never touched. Something correlated with it was, and the answer is only as good as the link between the two.
4 answersObserved once
A single recorded encounter. The record is real but the sample is one, so it establishes that something happened rather than how often.
4 answersReconstructed from fragments
A whole assembled from incomplete remains or partial records. Reconstruction is inference, and the missing pieces set the limits.