Validity

Validity is

• Construct validity
• Content validity
• Face validity

In psychiatry there is a particular issue with assessing the validity of the diagnostic categories themselves. In this context (Kendell):

   * content validity may refer to symptoms and diagnostic criteria;
   * concurrent validity may be defined by various correlates or markers, and perhaps also treatment response;
   * predictive validity may refer mainly to diagnostic stability over time;
   * discriminant validity may involve delimitation from other disorders.

To be valid, the result of a test has to accurately (i.e. reliably) answer the question that the test is intended to answer.

Reliability refers to consistency of a measuring instrument. Thus, reliability is necessary but not sufficient for validity. Inverse of reliability is "random error."

Measures of reliability include inter-rater reliability, test-retest reliability, and internal consistency reliability.

Further Reading

Kendell R. & Jablensky A. (2003) Distinguishing Between the Validity and Utility of Psychiatric Diagnoses Am J Psychiatry. January;160(1):4-12