IV] 



STATISTICAL STUDY 



39 



slope is measured by the size of the angle EOC. The 

 angle made by the diagonal at is 45°, the tangent 

 of which is 1 (unity). If there were no correlation 

 the angle would vanish, EF coinciding with CD, and 

 the correlation coefficient would be 0. Intermediates 

 are represented by the value of the tangent of the 

 angle EOC. In practice it rarely happens that the 

 points representing the means of the sons for each 

 class of fathers lie in a perfectly straight line ; when 

 they approach it closely the correlation is called 

 'linear'; when they depart from it considerably, it 

 is called ' skew.' 



Table of i/ntensitj/ of parental inheritance in different 

 species. [Froin Pearson.) 



