system. Recent research studies prove this assumption to be false, by showing that the addition of a predictor producing smaller group differences (i.e., personality test) to a predictor producing higher group differences (i.e., cognitive ability test) does not reduce the potential for adverse impact to the degree that is often expected (Bobko, Roth, & Potosky, 1999; Schmitt, Rogers, Chan, Sheppard, & Jennings, 1997). Although the use of personality tests with measures of cognitive ability may not have the desired effects on reducing adverse impact, it appears that the addition of personality measures to measures of cognitive ability as a composite predictor results in significant incremental validity (Bobko et al., 1999; Schmitt et al.,1997). These studies found that the validity of predictor composites was highest when alternative predictors were used in combination with cognitive ability. Though this combination of predictors resulted in the highest predictive validity, the inclusion of cognitive ability with these alternative predictors increased the potential for adverse impact (Steven L. Thomas & Wesley A. Scroggins, 2006). In summary, cognitive ability testing by itself has been shown to have high levels of validity, but comes with issues relating to adverse impact. Personality tests, on the other hand, have historically been proven to have low validity due to the lack of a common understanding on what constitutes personality, and the non-standardized measures available. But a growing number of research studies show that the best way for organizations to achieve close to optimal validity and job performance prediction, is to create a predictor composite that includes a measure of cognitive ability and an additional measure such as a personality test. Predictor validity and selection ratio Two major factors determine the quality of newly hired employees, predictor validity (aka predictive validity) and selection ratio. The predictor cutoff is a test score differentiating those passing a selection measure from those who did not. People above this score are hired or are further considered while those below it are not. If the test accurately differentiates between the successful and unsuccessful workers using this test score cutoff then it is high on predictor validity. The selection ratio (SR), on the other hand is the number of job openings n divided by the number of job applicants N. This value will range between 0 and 1, reflecting the selectivity of the organization's hiring practices. When the SR is equal to 1 or greater, the use of