2 EMPLOYMENT PSYCHOLOGY
rainstorm knocks the rear wheel off another car is obviously not
so much the cause of the accident as one who has the same sort
of accident on a bright, clear day. Likewise, icy pavements are
often the cause of accidents which are inexcusable in better
weather. What is careful and slow driving in one case will not
be so in the other. That, too, must be considered.
There are even other complicating factors, such as a careless
pedestrian stepping in front of the cab. Here the driver is not
the cause, yet technically he has had an accident. There may be
some unknown defect in the car mechanism which may cause an
accident. Again the driver is not the cause, yet technically he
has had an accident.
These, then, are the variables: To what degree is the driver
the cause of the accident? Should this be modified by the time
factor, or by the weather conditions? These are very pertinent
questions which must be dealt with in establishing criteria with
which to standardize the tests, to test them (correlate them with
actual fact), and to prorate them (determine their weight in
establishing a final score).
Even if we determine whether or not the driver is the cause,
it is impossible to discriminate finely the extent to which he is
the cause. This cannot be expressed numerically, nor can it even
be accurately expressed with a rating scale.
The legal department of the company, since it gets all the
original information—reports from the passengers and witnesses,
as well as from the drivers—attaches one of the three following
opinions to each accident: gross negligence, unavoidable, question-
able. Tt is this judgment we use in determining to what extent
the driver is the cause of the accident.
Snow’s success in applying the psychology of vocational
selection to the problem of choosing cab operators rests not
wholly on his ingenuity in devising and adapting tests. His
critical scrutiny of his criteria and his strict adherence to
them in planning his research and in evaluating its results
have likewise been important.
A criterion may be expressed in terms of a rough twofold
or threefold classification of the workers, or in terms of
such fine units of measurement that each man is distin-
guished from the others in accomplishment. If the criterion,
for example, is the amount sold in the course of a year,
the men may be separated into two groups: those who sold
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