IV 
40 
CHOICE OF WORKERS TO BE STUDIED 
Considerations in the choice of workers for study. Some disturbing variables 
to be eliminated. Newly hired versus old employees. 
THE criterion of vocational accomplishment having been 
settled upon, the investigator proceeds with the selection of 
workers or applicants whose abilities he is to measure. The 
choice must be made with due regard to the adopted cri- 
terion, so that a sufficient number of cases representing 
high, low, and average degree of success on the job will 
surely be included. 
REPRESENTATIVE SAMPLING 
The criterion which investigator and management have 
jointly agreed to use—as described in the previous chapter 
—may be output, length of service, rate of advancement, 
commission or bonuses earned, or a combination of these 
and other measures of actual vocational accomplishment. 
If this criterion is not kept in mind when the decision is 
made regarding the particular individuals whose abilities 
are to be the subject of investigation, the study is in danger 
of leading to inconclusive results. It is obvious that no 
relationships between test scores and actual abilities on the 
job can be established if all the workers tested are equally 
good at the job. In order to learn how well the tests or 
other measures differentiate the successes from the failures, 
good and poor workers must both be included. The sub- 
jects should be representative samplings within the criterion. 
Equal numbers of successes and failures should be chosen 
if possible; or if the criterion is threefold—successful, aver-