Agreement between a short form and the full scale as a function of the correlation between them

Much current research considers both correlational data and data on agreement in evaluating the usefulness of short forms of Wechsler's intelligence scales. It is demonstrated that when chance is excluded and disagreements are suitably weighted, the agreement between a short form and the Full Scale is simply an approximation to the correlation between them. Thus, the correlation itself should be the primary consideration in evaluating the usefulness of a short form.