EMPLOYMENT PSYCHOLOGY 
the well-known psychological tests, but to use any promising 
measuring device which may be made to conform to the 
principles set down in this and the preceding chapter. Proof 
of relationship between a series of measurements and suc- 
cess in an occupation makes that series of measurements, 
regardless of its origin, a matter of interest and value. 
Specialists in the selection of employees have installed sys- 
tems with a total disregard for scientific methods of validat- 
ing their results. Scientists who have evaluated the work of 
these persons have found most of it worthless. But some of 
these systems and tests show originality and, if applied with 
scientific care, might reward the investigator. If, on the 
other hand, they prove worthless, the investigator who has 
checked them scientifically instead of dismissing them with- 
out a hearing has a weapon with which to combat their 
advocates. 
The following chapters deal with the details of the con- 
struction of psychological tests, rating scales, and question- 
naires. 
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