# How The Scale Was Derived

The tests were arranged in order of difficulty, as found by trying them upon some

200 normal children of different ages from 3 to 15 years. It was found, for illustration,

that a certain test was passed by only a very small proportion of the younger

children, say the 5-year-olds, and that the number passing this test

increased rapidly in the succeeding years until by the age of 7 or

8 years, let us say, practically all the children were successful.

If, in our supposed case, the test was passed by about two thirds to

three fourths of the normal children aged 7 years, it was considered by

Binet a test of 7-year intelligence. In like manner, a test passed by

65 to 75 per cent of the normal 9-year-olds was considered a test of

9-year intelligence, and so on. By trying out many different tests in

this way it was possible to secure five tests to represent each age from

3 to 10 years (excepting age 4, which has only four tests), five for

age 12, five for 15, and five for adults, making 54 tests in all.

How The Scale Is Used How To Find The I Q Of Adult Subjects

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