Probability and utility assumptions underlying use of the Strong Vocational Interest Blank.

Decision implications of Strong's assumption of equal base rates for his men-in-gcncral (MIG) and individual occupational groups are explored. Using the Strong Vocational Interest Blank (SVIB) Physician's scale as an example, it is demonstrated that when realistic base rates are assumed, total decision error rate using the SVIB—even when optimal cutting scores are employed— is at best about equal to that resulting from prediction using base rates alone. It is shown that use of the SVIB as recommended by Strong implicitly assumes that false negative errors are much more serious than are false posi-tives. Finally, it is shown that when "reasonable " utility or gain matrices are assumed, use of the SVIB can reduce total error rate despite the limitations imposed by low occupational base rates, and that this effect is greater when statistically optimal cutting scores, rather than those recommended by Strong, are used. In many practical decision-making tasks faced by psychologists, scores on some con-