A psychometric investigation into the cross validation of an adaptation of the Ghiselli Predictability Index in personnel selection

Abstract

Twigge, Theron, Steele and Meiring (2004) concluded that it is possible to develop a predictability index based on a concept originally proposed by Ghiselli (1956, 1960a, 1960b), which correlates with the real residuals derived from the regression of a criterion on one or more predictors. The addition of such a predictability index to the original regression model was found to produce a statistically significant increase in the correlation between the selection battery and the criterion. To be able to convincingly demonstrate the feasibility of enhancing selection utility through the use of predictability indices would, however, require the cross validation of the results obtained on a derivation sample on a holdout sample selected from the same population. The objective of this article consequently is to investigate the extent to which such a predictability index, developed on a validation sample, would successfully cross validate to a holdout sample. Encouragingly positive results were obtained. Recommendations for future research are made.