EMPLOYMENT PSYCHOLOGY
(42) o=V Npq
N is the number of cases, p the proportion of these cases
giving one answer to the item, and ¢ the proportion giving
the other answer.
We have described the practical procedure to be followed
when the success of the applicant is to be predicted from a
measurement. The measurement may be a test score, a
questionnaire item, an interview rating, or any one of the
facts about an applicant’s personal history which can be
quantified and correlated with a criterion of successful accomplishment.
 In actual practice, probability of success is,
of course, usually predicted from a combination of such
items. The more information the better, provided its significance
 is known and not merely guessed at. When predicting
 success from a number of such measurements it is
necessary to combine them in such a way that the resulting
total score will have maximum predictive value. This procedure
 forms the subject of the next chapter.

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