The administrative officers of institutions may make rough estimates of the frequency of serious deficiency among their charges by regarding all over 14 as if they were 14 years of age or under, disregarding those under 12 years of age, tabulating the highest school positions reached, and finding the frequency of those four or more and five or more grades retarded below a standard of age 7 for the first grade. It would be well for each court also thus to make an estimate of the size of the problem of deficiency in its jurisdiction. According to the second suggestion which we have made, the Minneapolis Juvenile Court, for example, should plan to examine for mental deficiency all those two or more years retarded in school or about 20% of the boys found delinquent and nearly half of the girls. The prospect would be that the number sifted out as having feeble intellects will be less than 10% of the ordinary run of cases. Let us study a little further into the detention home cases tested by the Binet scale and see what additional light their school position throws upon the question whether or not they are defective delinquents. Four years retardation in school position would have called attention to both of our sure cases of feeble-mindedness. On the other hand, it would have brought in for examination only 4 out of the 7 doubtful cases. Three years of school retardation would have sifted out all but one. Two years school retardation, the rule suggested above, would have detected all those who tested doubtful. It would have required 56 examinations in this group to have found the eight cases suspicious under our test criteria. We also find that, among the random 15-year-olds not delinquent, examining all those 3 years retarded would have discovered all that tested even doubtful intellectually. Applying the rule that ability to carry seventh grade work is a good indication of a passable intellect, we find that none of our Glen Lake delinquents testing either presumably deficient or doubtful had reached the seventh grade. On the other hand, if one were disposed to object to saying that a person who passes Binet tests XI (1908) has a passable intellect, one finds in reply that 16 out of the 22 Glen Lake delinquent cases testing XI and three or more years retarded intellectually, _i. e._, presumably passable, were carrying seventh grade work or better. In examining individuals the importance of checking each of these tests with the other seems perfectly clear. If a boy fails in the Binet tests and shows better school ability one should certainly be cautious in his diagnosis. On the other hand a boy who is seriously behind in school may be found by the Binet scale to have a better intellect, so that the inquiry must be further extended to determine the cause of his school retardation. Retardation in school is generally not as fundamental a symptom of deficiency as retardation in the tests because of the numerous other causes of delay in school.