20 



KAEL PEARSON 



Left Foot 



a 



•iH 





Here 



Hence 

 and 



logx= = 2-9514, 



^(1 + a,) = -5410, 1(1 + a,) = -5047. 



Xa,= 1-2557, Xa,= 1-2534, 



Interpolation and the abac give us r = '72 and Macdonell has 76. The probable 

 error is only "Ol. These last two numbers on the assumption of a Gaussian 

 distribution. 



Illustration IX. I consider lastly a table which would by many be considered 

 to represent perfect correlation. 



Here log y^ = 3, 



i(l+a,)=i(l + a,) = -8, 



Xa, = Xa,= 1-4288; 



thus ocr,.= "064,557. 



The point on the abac is outside the contour r = "95, and some might be prepared 



on this account to consider the correlation as perfect. We must however proceed, 



as the value lies outside Table lY, by a slightly different method. By Table II, 



^2 = 1000 gives us 



-logP = 215-745, 



or logP = 2T6-255. 



We now turn back to equation (xvi) and note that 



s = _ = 239-946. 



