626 



MEMOIRS NATIONAL ACADEMY OF SCIENCES. 



[Vol. XV, 



gibly limited, and tests 4 and 7 extremely limited. Although the distribution of scores for 

 test 7 might be easily fitted with a Pearson type J curve, it seems clear that this would be a 

 sterile interpretation, for we can scarcely consider the type of reaction called for by test 7 to 



150- 



»oo- 



TE5TO, ALPHA 



250 



200 



150- 



100- 



50- 



50- 



lo 1 I I I 'to' I I ' W I ' I bo* l I I Uc 



TEST 5, ALPHA 



O 1 I • » '5' ' I I 'lO 1 ' l ' 'I6 1 I • I l 2 d » I I 



Flo. 3c. Histograms of scores in alpha tests. Special experimental Group X. 1,047 cases. Horizontal scale is score in test; vertical scale is number 



of cases. 



be of such specific nature as to justify an interpretation of discontinuity of "function" that 

 would be implied by the use of the type J curve. We must prefer to interpret all tests as different 

 methods of measuring a rather general capacity, and the histogram of test 7 exactly as we 

 interpret all others, as meaning incompleteness of the scale, in this case so extensive that only 

 individuals of approximately average intelligence or better can earn points. Beta tests (Fig. 4) 

 4, 5, 6, and 7 give histograms interpretable along exactly the same lines. Beta 7 displays limi- 

 tation of range at both ends. It may be remarked here that limitation of range may cause 

 massing of cases not only in the terminal class interval, but even in the adjoining ones, in some 



