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 ac- 
complishment. In actual practice, probability of success is, 
of course, usually predicted from a combination of such 
items. The more information the better, provided its sig- 
nificance is known and not merely guessed at. When pre- 
dicting 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 pro- 
cedure forms the subject of the next chapter. 
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