Maximizing prediction through combinations of predictors
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Here the organization has decided not to bother with the integrity test but to use two tests of extraversion plus the structured interview, perhaps because they think that extraversion is so important to this sales job. But there is a problem with this strategy. Using two tests of extraversion is not very helpful, because the two tests of extraversion are highly correlated with each other; in other words, they are redundant, and they basically explain the same areas of the job  performance criterion.
Structured Interview
Extraversion Test 1 and 2
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Job Performance Criterion for a Sales  Job
It’s important to have predictors that are correlated with job performance, but that are not highly correlated with each other. If they are too highly correlated with each other, they are redundant. To use redundant predictors in hiring costs money, and it’s inefficient.
Replay
As you can see in this figure, the three predictors – a personality test of extraversion, an integrity test, and an interview – each predict the criterion of sales performance. The three predictors are correlated with the criterion, and they are not very strongly correlated with each other. (Note that some overlap among predictors is unavoidable.)
Integrity Test
Extraversion Test