RATING SCALES :
An arbitrary value of 5 is given to all ratings in the upper
10%, 4 to the next 20%, 3 to the next 40%, 2 to the next
20%, and 1 to the lowest 10%. In this way each judgment
is expressed by comparison with the total, and the tendency
of any judge to underrate or overrate the group as a whole
is counteracted. In obtaining average or total ratings these
values are substituted for the original ratings. Other and
more refined methods are available, such as expressing each
rating as a deviation from the average rating given by the
judge, with the standard deviation of that judge’s ratings
as a unit. These statistical refinements should be avoided
when the groups are small, and should be used only when
the same group of men is rated by several judges.
When considering numerical ratings it is easy to lose
sight of the fact that they represent only relative standings
unless the zero point of the scale has been accurately deter-
mined. That A receives a rating of 25 and B a rating of
50 does not indicate that B is twice as able as A unless the
scale has been so constructed that a score of o represents
just not any of the ability, and the units of the scale are
equal to each other. In an experiment in selection it is not
necessary to make an accurate calculation of this zero point,
since relative position is our only objective. When deter-
mining the validity of the scale, a score is interpreted in
terms of the probable success of a person making the score.
It may be found that the above ratings indicated that B’s
chances of success are twice as great as A’s. This matter
will be discussed in Chapters XV and XVI.
To evaluate the analysis of abilities incorporated into a
rating scale, the ratings on these abilities may be compared
statistically with the criterion of success, in the same man-
ner as test scores. The statistical procedure involved is de-
scribed in Chapters XIII and XIV.
If the ratings on an ability for which a test cannot be
constructed correlate closely with the criterion of success,
the rating scale may be used as a part of the selection
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