XVII] 



(3) Houses in course of erection in 

 Urban and Rural Districts. 



Introduction xxxv 



(4) Imbecility and Deaf-Mutism. 



(5) Developmental Defects and Dullness. 



(f>- the mean square contingency = x 2 /iV an< ^ */> i s the product-moment coefficient 

 on the assumption that the 'presence of the character' is to be considered as 

 a concrete unit*. The coefficient of mean square contingency C. 2 = ^<p-/(l +4>°). 



The following table gives the values of %-, <f>-, j> and C' 2 , and the values of P 

 deduced. 



For example, from Table XVII by Formula (i) we have for x"= 1333265 : 

 (- log P) = 20-809 + ™™* [10-770] - J (^f 65 ) ( 1G ^ 5 ) [-026] 



= 27-985, 

 and therefore log P = 28-015, 



which leads to P = 1 -035/1 28 . 



Or again, for x~= 801462 : 



-V,p-i»«. + !*-p»«n- t @«)(^ [ « fl 



= 1738-498, 



* Pearson and Heron, Biometrika, Vol. ix. p. 167. 



(2 



