642 



MEMOIRS NATIONAL ACADEMY OF SCIENCES. 



[Vol. XV, 



Otherwise stated the variabilities of the groups in the alpha total score class intervals as measured 

 by a combination scale are given by 



Ik 



S =2, 

 so that for the class intervals in order we get : 



"M'R'J 



The variability for all class intervals above 35 points total score is constant. 



We next assume that these groups will be symmetrically distributed about their means, 

 and by means of Sheppard's tables distribute them according to the above set of standard 

 deviations. Table 159 is the final product of this procedure. 



Table 159. — Showing how the frequencies of each class interval of an alpha distribution should be disposed on the combined 



scale. 



In the case of the beta total scores we meet with difficulty owing to the lack of resemblance 

 of the score distributions of tests 1, 2, and 3 to the normal type. To analyze scores corre- 

 sponding to the mid-points of class intervals by methods deduced from the equations of a 

 normal system of variates would do too much violence to the facts to give a result of practical 



