Equating Logistic Ability Scales by a Weighted Least Squares Method

A general procedure for equating logistic ability scales that involves the use of a loss function and an optimization process is formulated. As one of the optimum estimation procedures, a weighted least squares method is introduced and applied to an achievement scale and an intelligence scale. An advantage of the method over previously proposed methods is that highly discriminating items tend to affect equating more strongly than less discriminating items.