Adverse impact and predictive efficiency of various predictor combinations

The effects of number of predictors, predictor intercorrelations, validity, and level of subgroup difference on composite validity adverse impact ratios, and mean subgroup difference associated with various predictor composites, including and excluding a ''high impact'' ability measure, were assessed. The size of subgroup differences is substantially smaller when low-impact predictors are combined with a high-impact predictor, but hiring ratios for majority and minority groups still indicate a prima facie case of discrimination, using the fourth-fifths rule for most predictor-criterion combinations. However, the validity of a composite of alternate predictors and cognitive ability may exceed the validity of cognitive ability alone and reduce the size of subgroup differences.