EMPLOYMENT PSYCHOLOGY 
angles. He must show, first, that the selective method he 
has devised has greater predictive accuracy than the meth- 
ods hitherto used in forecasting the vocational success of 
applicants. He must show, second, that when consideration 
is given both to cost of installation and operation of the 
selection methods and to increase in efficiency of operating 
departments resulting from selection of workers with higher 
vocational accomplishment, use of the new method will re- 
sult in a net economic saving. 
RELATIVE PREDICTIVE ACCURACY 
The methods of selection most commonly used in industry 
are of two sorts. They depend either on general impressions 
gained from application blank and personal interview or on 
the use of one of the many pseudoscientific methods of char- 
acter analysis. In either case it devolves upon the investi- 
gator to make an evaluation of the accuracy of prediction by 
these methods, employing the same rigorous procedure as in 
the evaluation of his own examinations, and using the same 
criterion of vocational accomplishment. Only under these 
conditions can a real comparison be made. 
If the interview is emphasized in the method of selection 
in use, the judgments of independent interviewers may be 
compared. In most instances the wide disagreement among 
interviewers will provide an opportunity for demonstrating 
the greater objectivity of tests. 
Wembridge (218) compared the validity of an intelligence 
test modeled upon Army Alpha and Beta with interviewers’ 
judgments of probable success. His subjects were several 
hundred machine operators in a clothing plant. The method 
of payment was that of piece rates with bonuses for a certain 
standard of quantity and quality. This standard was deter- 
mined by time studies and was applicable to all workers. 
The criterion of success was the percentage of this standard 
attained by the worker. The criterion and ratings by two 
216