Table 1.

Types of validity relevant to assessing “Truth”. From Felson. J Rheumatol 1993;20:531–4.

Type of ValidityMeaning
FaceCredibility: Is the instrument credible?
ContentComprehensiveness: Does the instrument (or group of instruments) sufficiently sample the core domain addressed?
ConstructDo the results of the instrument agree with expected results of other instruments measuring the same construct/concept?
CriterionDifficult in this setting. The only external criterion available is longterm outcome.
Does the result of the instrument predict or correlate with longterm outcome (e.g., death, disability, perhaps radiographic damage)?