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 pro- 
cedure depends as little as possible upon the skill of the 
examiner, and the whole matter proceeds almost automati- 
cally. This principle applies also to rating scales and ques- 
tionnaires. 
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. Mathe- 
matical 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 appara- 
tus or involved technique has these advantages: It is inex- 
pensive to construct; it requires less time to administer; it 
does not demand as much technical training of the exam- 
iner; 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 investi- 
gator 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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