Definition of "observational"

The essential fact is simply that all the pictures which science now draws of nature, and which alone seem capable of according with observational fact, are mathematical pictures.

1931, Sir James Hopwood Jeans, “Into the Deep Waters”, in The Mysterious Universe, Cambridge UP, page 111

An alternative way of defending the proposal to conflate NP MOVEMENT with XP MOVEMENT would be to question the observational adequacy of the claim that NP MOVEMENT only ever has NP constituents as its target.

1988, Andrew Radford, chapter 10, in Transformational grammar: a first course, Cambridge, UK: Cambridge University Press, page 535

No less than the novelist, the psychologist must employ techniques of literary construction to render scientific accounts acceptable. Most importantly, to the extent that such techniques dominate the scientific account, observational practices—regardless of rigor—cease to be influential.

1990, Kenneth J. Gergen, “Textual Considerations in the Scientific Construction of Human Character”, in Style, volume 24, number 3, page 366