Predictors should be combined to in

Predictors should be combined to increase the accuracy of a hiring decision according to the square of their validity coefficient. Suppose the mean validity of using an ability test alone is 53, and the mean validity of using an interview alone is. 14. By using an ability test and an interview together it is possible to raise the validity from 53 to 55, but only if the interview measures something more than the ability test and if the interview is weighted one fourteenth as much as the ability test(the predictors should be weighted proportionate to the square of the validity coefficients, i.e.. 532 and. 142). Of course, the validity of a specific selection process may be quite different than these averages.Expectancy ChartsExpectancy charts provide a method of illustrating the validity of a test and for interpreting test scores in terms of the probability of successful performance, Each bar on an expectancy percentage of the employees in a given predictor category are successful. Valid predictors typically produce expectancy charts with long bars for high predictor scores and short bars for low predictor scores as illustrated in Exhibit 19. Although expectancy charts show the same information that is reported by validity coefficients, expectancy charts are more useful in counseling employees since most employees do not understand correlation coefficients. The expectancy charts in Exhibits 19 and 20 are derived from the data in the following table3.