io6 



BIOMETRY 



straight line making an angle of 45 degrees with the 

 base line a line, that is to say, having a slope of 

 I in i, or unity ; whilst the entire absence of correlation 

 would be represented by a line having no slope that 

 is to say, a horizontal line. The actual result in the 

 example given is represented by a line having a slope 

 of nearly i in 2, or 0*5.* 



In the following table there are set down the corre- 

 lation coefficients for stature in the case of seven pairs 

 of relations, as obtained from actual data of a similar 

 character to that already given by Way of illustration. 



TABLE V. (FROM PEARSON). 



CORRELATION COEFFICIENTS FOR HUMAN STATURE. 



Father and son 

 Father and daughter . 

 Mother and son 

 Mother and daughter. 

 Brother and brother . 

 Sister and sister 

 Brother and sister 



0-514 

 0-510 



0-494 

 0-507 

 0*511 

 c'537 

 o'553 



Of the above, the first four values, representing 

 correlation between parents and children, are seriously 



* Correlated Variability. A precisely similar method Is 

 employed to measure the correlation of two parts or organs of 

 the same individual. For example, the lengths of the right 

 and left arms of men are very closely correlated. In order to 

 attach a numerical value to this correlation the lengths of 

 the right arms of a number of men are treated in the same 

 way as the statures of fathers in the example given, and the 

 lengths of their left arms in the same way as the statures of 

 sons. The proper correlation coefficient can then be found 

 by plotting the result ; or the labour of plotting may be 

 obviated by a process of calculation. 



