Discussion piece: The psychometric principles of assessment

Abstract

Psychometrics is the science of psychological assessment, and is a foundation of assessment and measurement. Within psychometrics there are four fundamental principles whereby the quality of an assessment is judged. These are (1) reliability, (2) validity, (3) standardisation and (4) freedom from bias. Reliability is the extent to which an assessment is free from error; validity is the extent to which a test or examination assesses what it purports to assess; standardisation gives us information on how the result of an assessment is to be judged; and freedom from bias examines the extent and causes of differences between groups. These four principles inform not only test use but also the entire process of test development, from the original curriculum or job specification, via the choice and appraisal of examination questions and test items, through to the eventual evaluation of the success or otherwise of the assessment itself.