The face validity of survey instruments and tests used in psychometrics, is assessed by cursory review of the items (questions) by untrained individuals. The individuals make their judgments on whether the items are relevant. For example, a researcher developing an IQ-test might ask his friends and relatives to read the questions and make their judgements.
The face validity is a qualitative measure of validity; it is not quantified with statistical methods. Of all validity measures, the face validity is normally considered as the least scientific measure – because untrained individuals chosen on the basis of convenience are involved, and because this measure is subjective and not quantifiable.