Karl Pearson and David Heron 
295 
method he uses some of Bateson and Saunders' data for Datura from the Report 
to the Evolution Committee, 1902 : 
Colour of Flower. 
Violet 
White 
Totals 
Prickly 
47 
21 
68 
Smooth 
12 
3 
15 
Totals 
59 
24 
83 
The difference of the cross products is 252 — 141 = 111 and then Mr Yule 
proceeds to tell us that " at first sight this considerable difference is apt to 
suggest a considerable association." He then divides by 83, and writes: "But 
& = 111/83 = 1'3 only, so that in point of fact the association is small, so small 
that no stress can be laid on it as indicating anything but a fluctuation of 
sampling" (p. 37). 
That Mr Yule is content with this process is evident from the opening words 
of the following paragraph : " While the methods used in the preceding pages 
suffice for most practical purposes, it is often very convenient to measure the 
intensities of association in different cases by means of some formula or 'coefficient'." 
We now know what Mr Yule considers "sufficient for most practical purposes"! 
Here are a few tables to illustrate it. 
(i) 
A 
Not-4 
Totals 
B 
Not-£ ... 
266,374 
233,626 
233,626 
266,374 
500,000 
500,000 
Totals ... 
500,000 
500,000 
1000,000 
(ii) 
A 
Not-J 
Totals 
B 
Not-5 ... 
934,579 
31,153 
31,153 
3,115 
965,732 
34,268 
Totals ... 
965,732 
34,268 
1000,000 
(iii) 
Not-J 
Totals 
B 
Not-B ... 
999,000 
450 
450 
100 
999,450 
550 
Totals ... 
999,450 
550 
1000,000 
