Predictor any variable used to forecast a criterion. Psychometric literally, the measurement ( metric ) of properties of the mind ( psychic ) it is the standard used to measure the quality of psychological assessments. If a predictor is not both reliable and valid, it is useless. Reliability: refers to consistency and stability, reliability the consistency, stability, or equivalence of a measure, a measure should yield the same estimate on repeated use if the measured trait hasn"t been changed, test-retest reliability. Reveals the stability of test scores upon repeated applications of the test. Simplest assessment of a measuring device"s reliability. Measure something at 2 different times and compare scores. Coefficient of stability: the higher, the more reliable the scores (~. 70 = acceptable) The shorter the interval between two tests, the higher the test-retest reliability coefficient: equivalent-form reliability. Reveals the equivalence of test scores between two versions or forms of the test.