THE METHOD OP AGE GRADATION 81 



varies only within the narrow range 0.71 to 0.77 for 

 the five years 8 to 12. Roughly expressed, therefore, 

 their intelligence, measured by that of normal per- 

 sons, is a ' three-quarter intelligence.' The imbeciles 

 show somewhat greater variations, but their mental 

 quotients are in quite fair agreement, at least for 

 the years 9 to 11. They entitle their possessors, 

 again roughly speaking, to a scant ' two-thirds intel- 

 ligence.' 



The first two of Chotzen's groups are represented 

 by too few cases to permit consideration of their 

 averages, save at most for the younger ages. In 

 these ages the mental quotient agrees finely with the 

 medical diagnosis of the children. Those desig- 

 nated as "not feeble-minded " have a mental quotient 

 of about 0.90, while the doubtfully-defective, whose 

 quotient lies between 0.80 and 0.84, form a real in- 

 termediate grade between the 'not-abnormal' and 

 the true morons. The isolated cases of older chil- 

 dren (7 in all) that Chotzen classified in these two 

 groups, are ranked by their quotient largely in the 

 morons. It is possible that the mental quotient may 

 supplement uncertain medical diagnoses in cases of 

 this sort. 



Now the objection might be raised to the above 

 series of quotients that they comprise only averages 

 and that these have been derived in part from a too 

 small number of values. To meet this objection I 

 have made another computation in which I have 

 worked out the mental quotients of individual chil- 

 dren, and then have recorded their frequency-dis- 

 tribution. In this computation I have disregarded 

 chronological age, and have combined in each case 



