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 (E) RELIABILITY OF THE TESTS

To measure the reliability of any newly devised test of intelligence is not a simple matter. It devolves upon the standardizer to present evidence that the new intelligence scale measures this inadequately defined entity 'intelligence' with approximately the same degree of accuracy as those standards or measuring 'rods' now commonly accepted and in current use.

In this brief article the writer will limit himself to five criteria:
 * (1) The mental processes employed;
 * (2) Increase in score from year to year;
 * (3) Correspondence of median mental ages;
 * (4) Correlations between mental ages, intelligence quotients and teachers' estimates of intelligence;
 * (5) Conformance of intelligence-quotient distribution with normal probability.

(1) Mental Processes Employed

In devising and standardizing this test the writer did not approach the problem with any bias of 'faculty psychology.' The idea still seems prevalent, though not as much now as in the immediate past, that in order to possess an adequate measuring instrument for intelligence, the device must contain separate tests for each mental 'function': sensation, perception, association, imagination, memory, judgment, reasoning, etc. On the other hand it has been amply demonstrated that the only intelligence scales worth the name draw service freely from all 'functions.' Binet has pointed out that all 'intelligent' operations involve the functioning of three primary activities: first, attention to the problem presented; second, a conscious attempt on the part of the subject to consummate an adequate adaptation to the situation; and third, the exercise of auto-criticism in order to determine how efficiently the specific 'adaptation' has solved the problem. A cursory examination of the demands made upon the mental operations of the person tested with the block-designs will clearly reveal that attention, adaptation and auto-criticism