SELECTION OF EXAMINATIONS
examiners. The test so administered becomes an unreliable
measure of the ability in question. The material of which
the test is composed, the conditions under which it is given,
the directions, the fore-exercises, the time limits, and the
method of scoring do not vary in a reliable test. The procedure
 depends as little as possible upon the skill of the
examiner, and the whole matter proceeds almost automatically.
 This principle applies also to rating scales and questionnaires.

The investigator should aim at maximum reliability in
the construction of his tests and should find out just how
reliable or unreliable they really are as instruments for
measuring the abilities they purport to measure. Mathematical
 procedures for determining reliability are outlined
in Chapter XIII.
Simplicity. Other things being equal, the simpler test is
the more desirable. A test requiring no complicated apparatus
 or involved technique has these advantages: It is inexpensive
 to construct; it requires less time to administer; it
does not demand as much technical training of the examiner;
 it does not frighten the applicant.
One advantage of an employment test is that it gives
immediately a prognosis of ability which otherwise would
require months on the job to disclose. The test record
should have the practical advantage that it is much easier to
obtain than the criterion. Simplicity should, therefore, be
constantly before the investigator as a desired characteristic
in his tests.
Analogy of test and ability to be measured. The investigator
 may wisely be guided in his selection of test materials
by their apparent relationship to the abilities required for
success. It is impossible to say in advance whether or not
a certain test measures a certain vocational ability. It is
probable, however, that a test which seems to measure that
ability will be more valid than one which seems to bear no
resemblance to it. If the abilities have been analyzed into

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