True Score

True score, which is the primary element of true score theory, is the individual's score on a measure if there was no error. Some classic theories of measurement believe that a true score can be estimated through repeated testing. The concept of true score is important to research design as it emphasizes that there is some error involved in any type of measurement (e.g., height, weight, self-esteem, IQ, and heart rate). In this entry, the definition of a true score is developed and explored with respect to reliability, measurement error, and classic extensions. Finally, some alternatives to true score theory are briefly presented.