VARIOUS USES OF FACTORS 61

problem is the typical problem of vocational selection, the
second the typical problem of vocational guidance.

Let us consider an actual example of vocational selection
first. An investigator desires to measure the predictive
value of a set of ' «estheto-kinetic ' tests that he has devised
for vocational selection. He may follow one of two pro-
cedures, which I have elsewhere called the ' analytic ' and
the c empirical' respectively.1 Adopting the * analytic '
procedure, he will, by special experiments or on the basis
of general impression, attempt a factorization first of the
performances involved in the vocational task, then of the
performances involved in the tests, with a view to showing
that the mental aptitudes required are essentially the same.
Probably he will begin by applying factorial or other methods
to analyse the measured skill of a group of trade workers
into its component mental functions. He finds, let us
suppose, that the chief functions are intelligence, sensory
discrimination, and motor dexterity. Accordingly, he
selects or constructs tests intended to measure these under-
lying abilities, applies them to a sample group of testees in
his laboratory, and demonstrates by factor-analysis that the
results of his tests depend essentially on the same three
factors as the trade skilL From this he infers that the set of
tests he has drawn up may be used to predict the vocational
success of future workers in the trade concerned.

With the * empirical' procedure he will apply his tests
directly to the workers themselves, and deduce a regression

1 I have ventured to abridge and quote passages from one or two early
memoranda drawn up while I was head of the Vocational Department of the
National Institute of Industrial Psychology. When that department was
first founded, it was my duty to draft a note on general principles for the first
investigations : and I am indebted to the Council of the Institute for
permission to make use of reports and other memoranda written while I
was working there. Like many other principles in vocational psychology
(which, owing to the difficulty of obtaining older children for experimental
research, can only be verified gradually and with difficulty) those described
in the text were in the first instance largely deduced as an application to
vocational problems of guiding ideas that had been found useful in previous
educational work. Though some of the suggestions proved impracticable,
the points here made have, I think, stood the test of experience. The
original arguments will be found set out in fuller detail in the chapter and
article cited below.