The term standard error of measurement indicates the spread of measurement errors when estimating an examinee’s true score from the observed score. Standard error of measurement is most frequently useful in test reliability. An observed score is an examinee’s obtained score, or raw score, on a particular test. A true score would be determined if this particular test was then given to a group of examinees 1,000 times, under identical conditions. The average of those observed scores would yield the best estimate of the examinees’ true abilities. Standard deviation is applied to the average of those scores across persons and administrations to determine the standard error of measurement. Observed score and true score can be used together to determine the amount of error:

$${\text{Score}}_{\text{true}}={\text{ Score}}_{\text{observed}}+{\text{ Score}}_{\text{error}}.$$

However, this true ...