CORRELATED VARIABILITY. 47 



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



1. 7195+1. 73J 



r 



\/2000 



The average variability of an array is =o\/lr 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 l is 



2 



the standard deviation of the subject, cr 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 ra t and n 3 are each less 

 than %n, so that n 2 contains the median. Let L lt L.+ be the 

 (unknown) distances of the mean from the two boundaries 

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



n, n. 2 n , 



AT'-" 1 * 



r 7T "0 



and 



