CORRELATED VARIABILITY. 47 



-W -i- =(2.5625-. 4535 X. 4605) 



*L7T95X 1.730 a=s - 7911 - 



A/2000 



The average variability of an array is =<r\/l r 2 . 

 The coefficient of regression marks the proportional 

 change of the relative organ for a unit's change of the sub- 



ject organ. It is given by the equation p=r , where a^ is 



<7 2 



the standard deviation of the subject, o 2 that of the relative. 



THE QUANTITATIVE TREATMENT OF CHARACTERS NOT QUAN- 

 TITATIVELY MEASURABLE. 



Even qualities that do not lend themselves to a quanti- 

 tative expression may be expressed in a roughly quantitative 

 fashion. The fundamental assumption is made that the 

 frequencies would obey the normal law of frequency more 

 or less closely, provided a quantitative scale could be found. 

 This assumption will not, in most biological data, lead us far 

 astray. 



Divide the data into three classes (e.g., in eye-color we may 

 have black, brown and gray, and blue), and let the frequency 

 of these classes be n } , n 2 , n. 3 , in which n t and n. 3 are each less 

 than \n, so that n 2 contains the median. Let L lf L. f be the 

 (unknown) distances of the mean from the two boundaries 

 of n 2 . Call L i /a=h l and L 3 /a=h 3 , then 



7T./0 



and 



n r +n 2 -n 3 

 n 



/2 f 

 V n J Q 



