Psychometrics is a 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, some psychometric researchers have, thus far, concerned themselves 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).