Psychometrics is the field of study concerned with the theory and technique of psychological measurement. One part of the field is concerned with the objective measurement of skills and knowledge, abilities, attitudes, personality traits, and educational achievement. For example, psychometric research has concerned itself with the construction and validation of assessment instruments such as questionnaires, tests, raters' judgments, and personality tests. Another part of the field is concerned with statistical research bearing on measurement theory (e.g., item response theory; intraclass correlation).
Thus psychometrics involves two major research tasks:
(i) the construction of instruments and procedures for measurement; and
(ii) the development and refinement of theoretical approaches to measurement.
Those who practice psychometrics are known as psychometricians. All psychometricians possess a specific psychometric qualification, and while most are psychologists with advanced graduate training in psychometric testing. Many work in human resources departments. Others specialize as learning and development professionals.