lii Tables for Statisticians and Biometricians [XXIX 



Hence the equation for r : 



- -000,6093 = -008,007?- + •006,072r- - -003,5727-^ 

 --003,3577-'. 

 Whence ?• = - 081 + -04.3. 

 Or, the association is not definitely significant. 



Illustration (iii). Find the tetrachoric r for the Table of Bradford Parents : 



Mother's Habits. 



ci i 



a 



CO 



Em 



Here a brief experience will show the reader that to proceed by tetrachoric 

 functions will require a very large amount of labour. 



We have 



HI - a.) = To =543/1696 = -32017; |(1 -«.,) = t„'= 63.5/1696 = -37441, 

 rf/iV= 476/1696 = -28066. 



We have accordingly the following series of tetrachoric functions — the first 

 6 from the table, the remaining 18 from the difference formula. 





Good 



Bad 



Totals 



Good 

 Bad 



994 ' 07 

 159 476 



1061 

 635 



Totals ... 



1153 543 



1696 



d^y 



i(l-a) 



1-1 



'"2 



'"3 



U 



l-u 



'"c 



-28066 



•32017 

 •37441 



-35769 

 ■37901 



•11817 

 •08581 



-■11415 

 - •13887 



- -09489 

 -■07178 



•05674 

 •08288 



-08012 

 -06325 



'■7 



rs 



rg 



TlO 



Tn 



TVI 



Tu 



Tl4 



- -02963 



- -05629 



- -06913 

 - -05709 



-01368 

 -04034 



•06032 

 •05223 



- ^00324 



- -02957 



- -05294 



- -04819 



- -00401 

 -02176 



-04659 



•04558 



T-is 



no 



m 



T18 



ri9 



T20 



rn 



T22 



•00922 

 - -01575 



- -04103 



- -04245 



- -01304 

 -01103 



•03609 

 •03966 



-01586 

 - -00723 



- -03167 



- ^037 14 



- -01793 

 -00411 



•02768 

 -03484 



r-a 



TU 



h 



— 



— 



— 



— 



— 



•01944 

 - -00151 



- -02407 



- -03272 



-46732 

 •32020 



— 



— 



— 



— 



— 



