Psychological testing is the administration of psychological tests, which are designed to be “an objective and standardized measure of a sample of behavior”. The term sample of behavior refers to an individual’s performance on tasks that have usually been prescribed beforehand. The samples of behavior that make up a paper-and-pencil test, the most common type of test, are a series of items. Performance on these items produce a test score. A score on a well-constructed test is believed to reflect a psychological construct such as achievement in a school subject, cognitive ability, aptitude, emotional functioning, personality, etc. Differences in test scores are thought to reflect individual differences in the construct the test is supposed to measure. The science behind psychological testing is psychometrics.