Design of Experiments > Face Validity
What is Face Validity?
Face validity, also called logical validity, is a simple form of validity where you apply a superficial and subjective assessment of whether or not your study or test measures what it is supposed to measure. You can think of it as being similar to “face value”, where you just skim the surface in order to form an opinion. It is the easiest form of validity to apply to research. However, it doesn’t general include much (if any at all) in the way of objective measurements. Therefore, it is often criticized as the weakest form of validity.
For example, IQ tests are supposed to measure intelligence. The test would be valid if it accurately measured intelligence. Very early IQ tests would often have pictures of missing items, like a missing tennis ball from a court, or a missing chimney from a house. At face value, the test was thought to be valid and fair to speakers of languages other than English, because pictures are a universal language. However, the test was actually biased against the poor, who may not have ever seen a tennis court. It was also biased against people from some Christian countries who thought a cross was missing from the roof, not a chimney.
Why is Face Validity Used?
If face validity is the weakest form of validity, why use it at all? One reason is to quickly eliminate shoddy research. For example, let’s say a researcher’s work indicated that drinking milk caused colon cancer. A peer review of the paper by a distinguished biochemist revealed several shortcomings in the design of the experiment. The biochemist rejected the paper on face validity, but they were well qualified to do so. In essence, face validity is weaker for a layperson, and stronger for an expert in the field.