10 



EMPIRICAL STUDIES OF MEASUREMENT 



variability, but that one law obtains for stature and another for 

 span or finger length, then a fortiori no constant relation can be pre- 

 supposed when the variability of a group in one trait is to be com- 

 pared with its variability (or that of a second group) in a different 

 trait. 



The first facts to which I call the reader's attention are the com- 

 parison of arrays of y corresponding to very low values of x with 

 arrays of y corresponding to very high values of x in the case of ten 

 correlations chosen at random (so far as this issue is concerned) 

 from Vols. I. and II. of Biometrika. The number of cases ranged 

 from 49 to 319. The results are given in Table V. in the form 

 of (1) the variability of arrays related to high central tendencies of 

 x (and consequently having high central tendencies of y) divided 

 by the variability of arrays related to low central tendencies of x, 

 under the heading 'Gross'; (2) the Pearson coefficient of variability 

 for the former divided by the Pearson coefficient of variability for 



the latter under the heading ; and (3) the similar ratio for the 



1 



two variabilities each having been divided by the square root of the 

 amount of the corresponding central tendency, under the heading 



==. A perfect method would give values of 100 throughout. 

 VC.T. 



Width of head 



Length of left middle finger 



Number of stamens 



Number of stamens 



TABLE V. (a) 



Gross. 



101.5 



94.4 



112.3 



Frontal breadth 



Length of right antenna (aphis) 



Number of stamens 



164.7 



106.8 

 88.2 

 111.6 



Number of stamens (lesser celandine) 132.6 



Span 



Forearm length 



Median 



115 

 95.7 

 109.2 



Gross 

 C.T. 



95.7 



89.5 

 110 

 86 



90.8 

 106 

 99 



90.1 



I/ C.T. 

 98.5 



96.3 

 135 

 96.1 



100.8 



119 



107 



97.5 



Nearest to 

 Equality. 



Gross 



VC.T: 



Gross 

 Gross 



Gross 

 C.T. 



Gross 



Gross 

 Gross 



Gross 



C.TT 



Gross 



Gross 



The detailed facts from which these ratios come are given in Table V. (6). 



