THE PROBLEM OF SELECTION
for the investigation. This choice will be determined in
part by practical considerations and in part by the criterion
of vocational success which has been agreed upon.
The investigator then proceeds to determine at least pro-
visionally the abilities most essential for success. This step
is facilitated by having for observation the workers who
have been chosen as subjects for the investigation.
In the light of his analysis the investigator selects or
devises psychological tests, questionnaires, rating scales, or
other examinations which give promise of measuring these
essential abilities.
Under carefully controlled conditions the investigator next
applies these means of measuring abilities to the subjects
chosen for the investigation.
At or before this stage of the research the reliability of the
examinations should be determined. A test or rating scale
which does not give the same results upon repeated trials is
as unreliable for purposes of vocational selection as an
elastic tape would be for measuring stature.
After the reliability of the examinations has been ascer-
tained, their validity as indicators of success in the vocation
is determined. The investigator validates a measuring
instrument by comparing his measurements with the cri-
terion of vocational success. A device is valid and useful
which yields measures so closely related statistically to the
criterion of success that, knowing a person’s score, his
degree of success in the occupation may be at least roughly
foretold. The value of the examination depends upon the
closeness with which it predicts the vocational success of the
applicant.
The next step in the research is to find what combination
of the several examinations which have proved to be valid,
yields a total score with a maximum predictive value.
The investigator will then have to justify this battery of
tests or other aids in selection by comparing its predictive
accuracy with that of the methods of selection previously
In use.
