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External Validity is a form of experimental validity An experiment is said to possess external validity if the experiment’s results hold across different experimental settings, procedures and participants [2,3. If a study possesses external validity, its results will generalize to the larger population.
The most common loss of external validity comes from the fact that experiments using human participants often employ small samples obtained from a single geographic location. Because of this, one can not be sure that any results obtained would apply to people in other geographic locations.
External vs. Ecological Validity
External validity should not be confused with ecological validity. While external validity deals with the ability of experimental results to generalize to the “real-world” population, ecological validity is possessed when the experimental procedures resemble real-world conditions. While these forms of validity are closely related, they are independent--a study may possess external validity but not ecological validity, and vice-versa.
See also
- Internal validity
- Construct validity
- Content validity
- Statistical conclusion validity
- Ecological validity
References
* Mitchell, M. and Jolley, J. (2001). Research Design Explained (4th Ed) New York:Harcourt.
* Brewer, M. (2000). Research Design and Issues of Validity. In Reis, H. and Judd, C. (eds) Handbook of Research Methods in Social and Personality Psychology. Cambridge:Cambridge University Press.
* Shadish, W., Cook, T., and Campbell, D. (2002). Experimental and Quasi-Experimental Designs for Generalized Causal Inference Boston:Houghton Mifflin.
"External validity"