VIII IX I 



Ixxv 



Wo have = '3072, </> = '6928, x = -8063, i/r--1937. 

 Thus *,= a341,9536gg^595.0464 



,(191,979) (-176,847) 



The observed value of d/^V occurs in the h = '4 to '5 and k = '3 to *4 in the 

 ?* tables for '45, '50 and '55; we therefore try r = '50 first, i.e. the upper numbers 

 in the curled brackets, and find d/N = '190,1206 too small; we then compute for 

 the higher number r='55, i.e. the lower figures. These give us d{N = '198,4860. 

 Interpolating linearly for d/N = '196,3190, we have 



The value found from the full tetrachoric equation is r = '5370, in exact agree- 

 ment. Thus the hyperbolic formula appears quite adequate in this case. 



Illustration (xiv). Habits of Mother and Cleanliness of Home. (Bradford.) 



Habits of Mother 



Here 



and 



(1 - a h ) = -320,165, \ (1 - a h ) = -308,373, 



d/N= -223,4670. 

 Hence h = '46724, k = '50047. 



We have = '6724, </> = '3276, x = '0047, -^ = '9953. 

 The value of djN occurs in the (h, k) range for r = '80 and r = '85 only. It is 

 sufficient therefore to interpolate into these tables. We have 



_ (-223,2955) 

 "[235,6484] ' 

 Hence, interpolating for the observed value of d/N, we find 



I 71 K 



Using 18 tetrachoric functions and adjusting for the remainder we find r ='8001 3. 



