writer).

METHOD OF ARRIVING AT A REVISION. The revision of the scale below
the 14-year level was based almost entirely on the tests of the
above-mentioned 1,000 unselected children. The guiding principle was to
secure an arrangement of the tests and a standard of scoring which would
cause the median mental age of the unselected children of each age group
to coincide with the median chronological age. That is, a correct scale
must cause the _average_ child of 5 years to test exactly at 5, the
_average_ child at 6 to test exactly at 6, etc. Or, to express the same
fact in terms of intelligence quotient,[16] a correct scale must give a
median intelligence quotient of unity, or 100 per cent, for unselected
children of each age.

[16] The intelligence quotient (often designated as I Q) is the ratio of
mental age to chronological age. (See pp. 65 _ff._ and 78 _ff._)

If the median mental age resulting at any point from the provisional
arrangement of tests was too high or too low, it was only necessary to
change the location of certain of the tests, or to change the standard
of scoring, until an order of arrangement and a standard of passing were
found which would throw the median mental age where it belonged. We had
already become convinced, for reasons too involved for presentation
here, that no satisfactory revision of the Binet scale was possible on
any theoretical considerations as to the percentage of passes which an
individual test ought to show in a given year in order to be considered
standard for that year.

As was to be expected, the first draft of the revision did not prove
satisfactory. The scale was still too hard at some points, and too easy
at others. In fact, three successive revisions were necessary, involving
three separate scorings of the data and as many tabulations of the
mental ages, before the desired degree of accuracy was secured. As
finally revised, the scale gives a median intelligence quotient closely
approximating 100 for the unselected children of each age from 4 to 14.

Since our school children who were above 14 years and still in the
grades were retarded left-overs, it was necessary to base the revision
above this level on the tests of adults. These included 30 business men
and 150 "migrating" unemployed men tested by Mr. H. E. Knollin, 150
adolescent delinquents tested by Mr. J. Harold Williams, and 50
high-school students tested by the writer.

The extension of the scale in the upper