Validity refers to the extent to which a concept or measurement accurately reflects what it is intended to measure. Types of validity include:
Predictive Validity: The degree to which a test or diagnosis accurately predicts future outcomes, such as treatment effectiveness.
Face Validity: The degree to which criteria appears, at face value, to measure what it says it measures. This may be subject to social desirability bias.
Construct Validity: The degree to which a diagnostic questionnaire actually measures the disorder it intends to measure. This is established by administering the test to people who were previously diagnosed.