Difference between revisions of "Validity"

Revision as of 21:35, 9 September 2012

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.

In psychiatry there is a particular issue with assessing the validity of the diagnostic categories themselves.

In this context:

• Construct validity includes (at least) content, discriminant, and convergent validity. It answers the question: Are we measuring what we want to measure?
  • content validity refers to symptoms and diagnostic criteria, i.e. how well the test measures all aspects of a phenomenon;
  • discriminant/convergent validity assess if symptoms or properties that are suppose to be different/same are found to be different/same with a particular test.
• concurrent validity refers to weather a test correlates well with a measures that had previously been validated.
• predictive validity refers mainly to diagnostic stability over time;

Further Reading

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

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