XXXIV 



Tables for Statisticians and Biometricians 



[XVII 



Table XVII (p. 31) 



Values of (— log P) corresponding to given values of ^ in a fourfold table. 

 (K. Pearson : On a Novel Method of regarding the Association of two Variates 

 classed solely in Alternate Categories. Drapers' Company Research Memoirs, 

 Biometric Series, viii. Dulau & Co.) 



If individuals be classed by the characters into A and not-.4, B and not-5, we 

 form a tetrachoric table of the form 



For such a table : 



% 2 = 



N(ab-cdf 



(a + b) (c + d)(b + d)(a + c)' 



.(xxxi), 



gives a measure of the probability of independence, and, if the two attributes are 

 highly associated, %" will be large and P the probability of independence very 

 small and largely outside Palin Elderton's Table XII. Tabic XVII provides for 

 such cases. 



Illustrations. The following tables are given by Mr G. U. Yule in his Theory 

 of Statistics*. His conclusions with regard to them are: 



1. Datura : " No Association." 



2. Eye Colour in Father and Son : " Shows the tendency to resemblance." 



3. Houses in course of erection, Urban and Rural : " Distinct Positive 

 Association." 



4. Imbecility and Deaf-Mutism : " High Degree of Association." 



5. Developmental Defects and Dullness : " Very high indeed." 



It is required to measure the degree of probability that the variates in these 

 five cases are independent. 



(1) Datura. (2) Eye-Colour in Father and Son. 



Colour of Flower. Father. 





a 

 o 



* Pp. 37, 34, 62, 33, 34 and 45 respectively. 



