Face validity is the assessment of whether or not a test seems OK. Or (subjectively) whether it ‘should be valid’, possibly as a result of an analysis of the meaning of the words used. Questions of the form ‘how good are you at arithmetic’ or ‘do you suffer from depression’ represent weak tests of validity. Answers may be correct but they may easily be wrong if people only partially understand the implications of the concept or (consciously or unconsciously) deny or exaggerate the truth. A better test of depression would ask unthreatening questions about behaviour which covered each of the major symptoms of depression – sadness, pessimism, guilt, tiredness, lack of energy, poor sleep, etc. This would increase confidence in content validity. The Beck Depression Inventory asks 21 such questions without mentioning ‘depression’. The McGill Pain Inventory isolates 20 possible facets of pain quality also without mentioning pain, its intensity or duration.