Face validity, as the name suggests, is a measure of how representative a research project is 'at face value,' and whether it appears to be a good project.
Whilst face validity, sometime referred to as representation validity, is a weak measure of validity, its importance cannot be underestimated.
This 'common sense' approach often saves a lot of time, resources and stress.
The difference is that content validity is carefully evaluated, whereas face validity is a more general measure and the subjects often have input.
An example could be, after a group of students sat a test, you asked for feedback, specifically if they thought that the test was a good one. This enables refinements for the next research project and adds another dimension to establishing validity.
Face validity is classed as 'weak evidence' supporting construct validity, but that does not mean that it is incorrect, only that caution is necessary.
On the other hand, a distinguished climatology professor could read through it and find the paper, and the reasoning behind the techniques, to be very poor.
This example shows the importance of face validity as useful filter for eliminating shoddy research from the field of science, through peer review.
Especially in the social and educational sciences, it is very difficult to measure the content validity of a research program.
Often, there are so many interlinked factors that it is practically impossible to account for them all. Many researchers send their plans to a group of leading experts in the field, asking them if they think that it is a good and representative program.
This face validity should be good enough to withstand scrutiny and helps a researcher to find potential flaws before they waste a lot of time and money.
In the social sciences, it is very difficult to apply the scientific method, so experience and judgment are valued assets.
Before any physical scientists think that this has nothing to do with their more quantifiable approach, face validity is something that pretty much every scientist uses.
This is face validity in action.
Babbie, E.R. (2007). The Practice of Social Research. Belmont, CA: Wadsworth Cengage Learning
Gatewood, R.D., Feild, H.S., & Barrick, M. (2008). Human Resource Selection (6th Ed.). Mason, OH: Thomson
Polit, D.E., & Tatano Beck, C. (2008). Nursing Research : Generating and Assessing Evidence for Nursing Practice (8th Ed.). Philadelphia, PA: Lippincott Williams & Watkins