spell, to write unusual words, to file letters and to find letters
in a file. On the basis of this wider knowledge we construct a
series of performance tests which take, say, half an hour for any
stenographer to go through. We may find that our first test is
entirely too complicated and that only three or four of the best
individuals in a large typewriting office can pass it. But we are
just as likely, on the other hand, to make a test which is too easy,
so easy indeed that even the poorest members of the group can
pass it. We then work at the method until the average good
stenographer can pass the test. Naturally the test must be
constructed with reference to the field of general stenographic
work. This test would not be suitable for accountants, for news-
paper reporters or for any other vocational field. Such work
is being done constantly by many business houses in consultation
with psychologists. Indeed, many of the larger business houses
now employ psychological experts for devising such tests. The
construction of the test is a research problem. The use of the
test can possibly be left to individuals who are not psychologists,
but who may have received special instructions in its use.

A slightly different task it at hand when we have to ask the
question: What are the general factors which enter into the
make-up of a successful lawyer, statesman, newspaper corre-
spondent, or aviator. We may say in advance that no very ser-
viceable correlations throwing light upon such questions have
yet been obtained. To make the problem specific we may take
up the study of the make-up of a successful aviator: What factors
in the previous life of the aviator make for success in flying?
Has the amount and kind of academic education anything to do
with it? The stratum of society from which he comes, age, pre-
vious occupation and salary obtained in it, marriage, and athletic
attainments? To answer the question the necessary data are
obtained from successful and unsuccessful pilots. The material
so obtained is then subjected to statistical treatment and the
co-efficients of correlation obtained.³

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