CORRELATION 



101 



the case of characters which can be shown to vary 

 normally. The method of calculation actually em- 

 ployed involves somewhat complicated mathematical 

 processes, but on Professor Pearson's authority we 

 may assume both the validity of the method and the 

 accuracy of the results obtained so far as the actual 

 process of computation is concerned. For the purpose 

 of making the necessary calculations the data were 

 arranged in such a form as the following : 



PARENTAL CORRELATION OF COAT COLOURS IN HORSES. 



By the suitable treatment of these figures the 

 value 0*45 was obtained as representing the coefficient 

 of correlation between sire and filly. 



The amount of reliance which is to be placed in the 

 above method of determining the value of a correlation 

 coefficient was tested by arranging in a similar manner 

 data with regard to stature which had already been 

 treated in the form of a complete correlation table. 

 The whole number of fathers was divided into two 

 groups containing the individuals above and below a 

 certain stature, and the same was done in the case 



