VIII IX] 



Introduction 



Ixxiii 



could only occur when h is slightly greater than '50. Working with the '45 and ">0 

 table we have 



+ -0014,7204 |;J^361| + . 0032>2796 



_ (-146,4758) 

 " |-153,9025J ' 

 Interpolating linearly we have 



The value found from the full tetrachoric equation is "4524. 



Or, the agreement is complete without passing to second order differences. 



Illustration (xii). Eye Colour in Brother and Sister. 



Brother 



Here 



(1 _ Kh ) = -394,000, |(1 - a*) = -443,333, 



d/N= -248,0000, 

 and & = -26891, k = 14253. 



This value of djN can lie in the '40, '45, or -50 tables for r, we therefore start 

 by interpolating into that for r = '45. We have 



#=6891, 6 = '3109, % = -4253, ^ = '5747. 



Hence 



_ (-245,9393) 

 Ze >* ~ |-254,6369j ' 



the upper number showing that we need r = '50, and not "40. 

 Thus by linear interpolation 



20607 



The actual value of r is '4614. 



B. II. 



