What does "external validity" refer to?

External validity refers to the extent to which the results of a study can be generalized beyond the specific conditions or population that were studied. It is concerned with how well the findings can apply to other settings, populations, or times. This concept is crucial in research because a study may have strong internal validity—meaning it reliably measures what it intends to—but if the findings cannot be reasonably applied outside the study's specific context, their practicality in real-world situations is limited.

For instance, if researchers conduct a clinical trial in a controlled environment with a specific group of people, the external validity examines whether the results can be considered relevant to broader or different groups of people or other settings that were not part of the study. Understanding external validity is essential for clinicians, policymakers, and researchers who want to apply study findings to different populations or situations.