EMPLOYMENT PSYCHOLOGY
It has been customary to draw various lines of distinction
between psychological tests and psychological experiments. Some
of these distinctions have broken down in practice. It is not
strictly correct to state that a test dispenses with the typical
precautions in control of conditions deemed essential in a laboratory
 experiment; nor that only the experiment utilizes instruments
of precision. Nor is it always strictly true that an experiment is
performed to try out an hypothesis and establish a generalization
while a test is limited in its purpose to the measurement of the
individual. Terman (186) in his presidential address before the
American Psychological Association effectually disposed of that
tradition by assembling the general principles of psychology which
have been ‘developed by means of research with tests.
In the foregoing chapter several features of a good vocational
 test were outlined. It should be simple in conception
and operation. It should be constructed so as to yield an
objective quantitative measure which does not vary with
the person who administers or scores it. Its material, the
conditions under which it is given, the directions, and the
method of scoring should be rigidly specified and adhered to,
so that scores made by persons examined at different times
and places will be comparable. It should be built on the
theory that it measures one or more of the abilities necessary
 to the job. It should have an apparent relevance to
the job requirements to insure the applicant’s interest.
Chapter V discusses the ways of arriving at the abilities
which the tests should aim to measure. In constructing a
test for one of these abilities, the investigator will find it
profitable to refer to the sources of test material listed in
Chapter VI. He will also find it highly worth while to consult
 all relevant material on test construction and application
 gathered by other psychologists, especially where they
have studied the same or similar vocations. Above all, he
should hesitate to develop a new test if he can find one
already available. Unless he makes a decided improvement
on an existing test he will do little more than add to the
growing profusion of insufficiently evaluated and hence useless
 psychological tests.

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