Reliability

There are several definitions of reliability for measures of individual differences, each stressing one of its many facets. It may be defined as the accuracy or precision of an instrument in measuring the “true” standing of persons to whom a particular test was administered. Another definition states that reliability is an estimate of the stability, dependability, or predictability of a measure. This definition focuses on whether repeated measures taken on the same persons using the same or comparable instruments will produce the same or similar results. Finally, reliability is defined as the proportion of observed score variance that is attributable to true score variance.