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 should measure very largely the reliability of the newly devised tests.

In the following table this comparison is presented:

Four important items are worthy of note: In the first place, the average deviation of the median Binet ages from the life ages at each year is 6 months; second, the average deviation of the median block-design ages from the life ages at each year is 8.8 months; third, the average deviation between the two intelligence-test medians is 8 1/2 months, and finally, the arithmetic mean of the two medians for each life age results in a more accurate approximation of what may be the 'true' mental age than either median taken alone. The significance of the last fact will have to be left for more complete discussion in the later monograph. At this point, it may be sufficient to remark that the approximation between the Binet and block-design medians is rather close, especially when we consider that the block-design tests are quite free of the 'language factor.'

(4) Correlations between Mental Ages, Intelligence Quotients and Teachers' Estimates of Intelligence

In order to understand and to justly evaluate the relations about to be presented, the Binet results will be mentioned to serve as a standard of comparison.