Psychometric properties

Psychometric properties refer to the validity and reliability of patient-reported outcome measurement tools. Before being able to state that a questionnaire has excellent psychometric properties, meaning a scale is both reliable and valid, it must be evaluated extensively. Reliability is the degree to which a measure is free from measurement error and includes internal consistency reliability and test-retest reliability. Validity is the degree to which an instrument measures the outcome concepts it purports to measure and includes content validity, construct validity, criterion validity and responsiveness.