Childs and
Terman in 1910-11, and of 300 children by Trost, Waddle, and Terman in
1911-12. For various reasons, however, the results of these tests did
not furnish satisfactory data for a thoroughgoing revision of the scale.
Accordingly a new investigation was undertaken, somewhat more extensive
than the others, and more carefully planned. Its main features may be
described as follows:--

1. The first step was to assemble as nearly as possible all the results
which had been secured for each test of the scale by all the workers of
all countries. The result was a large sheet of tabulated data for each
individual test, including percentages passing the test at various ages,
conditions under which the results were secured, method of procedure,
etc. After a comparative study of these data, and in the light of
results we had ourselves secured, a provisional arrangement of the tests
was prepared for try-out.

2. In addition to the tests of the original Binet scale, 40 additional
tests were included for try-out. This, it was expected, would make
possible the elimination of some of the least satisfactory tests, and at
the same time permit the addition of enough new ones to give at least
six tests, instead of five, for each age group.

3. A plan was then devised for securing subjects who should be as nearly
as possible representative of the several ages. The method was to select
a school in a community of average social status, a school attended by
all or practically all the children in the district where it was
located. In order to get clear pictures of age differences the tests
were confined to children who were within two months of a birthday. To
avoid accidental selection, _all_ the children within two months of a
birthday were tested, in whatever grade enrolled. Tests of foreign-born
children, however, were eliminated in the treatment of results. There
remained tests of approximately 1000 children, of whom 905 were between
5 and 14 years of age.

4. The children's responses were, for the most part, recorded
_verbatim_. This made it possible to re-score the records according
to any desired standard, and thus to fit a test more perfectly to the
age level assigned it.

5. Much attention was given to securing uniformity of procedure. A
half-year was devoted to training the examiners and another half-year to
the supervision of the testing. In the further interests of uniformity
all the records were scored by one person (the