Final answer:
Population validity is the type of validity concerned with generalizing study results to different populations, as opposed to ecological or temporal validity.
Step-by-step explanation:
The type of validity that is concerned with the extent to which the results of a study can be generalized to, and across, different populations is known as population validity. Population validity focuses on the representativeness of the sample and whether the findings can be applied to the wider population beyond the study participants. This differs from ecological validity, which is concerned with how well a study’s findings can be generalized to real-world settings, and from temporal validity, which deals with the generalization of findings over time.