evel of intelligence. A great
many tests are required; and for two reasons: (1) because intelligence
has many aspects; and (2) in order to overcome the accidental influences
of training or environment. If many tests are used no one of them need
show more than a moderately high correlation with the scale as a whole.
As stated by Binet, "Let the tests be rough, if there are only enough of
them."

CHAPTER VI

THE SIGNIFICANCE OF VARIOUS INTELLIGENCE QUOTIENTS

FREQUENCY OF DIFFERENT DEGREES OF INTELLIGENCE. Before we can interpret
the results of an examination it is necessary to know how frequently an
I Q of the size found occurs among unselected children. Our tests of
1000 unselected children enable us to answer this question with some
degree of definiteness. A study of these 1000 I Q's shows the following
significant facts:--

The lowest 1 % go to 70 or below, the highest 1 % reach 130 or above
" " 2 % " " 73 " " " " 2 % " 128 " "
" " 3 % " " 76 " " " " 3 % " 125 " "
" " 5 % " " 78 " " " " 5 % " 122 " "
" " 10 % " " 85 " " " " 10 % " 116 " "
" " 15 % " " 88 " " " " 15 % " 113 " "
" " 20 % " " 91 " " " " 20 % " 110 " "
" " 25 % " " 92 " " " " 25 % " 108 " "
" " 33+1/3% " " 95 " " " " 33+1/3% " 106 " "

Or, to put some of the above facts in another form:--

The child reaching 110 is equaled or excelled by 20 out of 100
" " " (about) 115 " " " " " 10 " " "
" " " " 125 " " " " " 3 " " "
" " " " 130 " " " " " 1 " " "

Conversely, we may say regarding the subnormals that:--

The child testing at (about) 90 is equaled or excelled by 80 out of 100
" " " " " 85 " " " " " 90 " " "
" " " " " 75 " " " " " 97 " " "
" " " " " 70 " " " " " 99 " " "

CLASSIFICATION OF INTELLIGENCE QUOTIENTS. What do the above I Q's imply
in such terms as feeble-mindedness, border-line intelligence, dullness,
normality, superior intelligence genius, etc.? When we use these terms
two facts must be borne in mind: