The extent to which the results of a research study apply to situations beyond the study itself, and the extent to which conclusions can be generalized, is

External validity is the extent to which results apply beyond the study and can be generalised.

Internal validity instead concerns accurate causal inference within the study itself.

Situational validity is not a standard recognised category of validity.

Face validity merely judges apparent relevance on the surface.

External validity asks whether findings hold across people, settings and times.

Random sampling and representative samples strengthen it.