Ixxvi 



Tables for Statisticians and Biometricians [VIII IX 



The labour of determining and solving an equation of this order is very great, 

 and we cannot even then be absolutely sure to a unit in the fifth figure of r. We 

 accordingly proceed to a more close interpolation from the tables. We need the 



following S 2 's and S /2 's : 



- 



- -001,305 



- -001,077 



- -001,279 



- -001,116 



- -000,989 



- -001,077 



- -000,648 



- -000,795 

 Using formula (/3) we have for the remainder 



R = - (-6724 x -3276) 

 - -0367,1304 



r=-85 



- -001,695 



- -001,454 

 --001,633 



- -001,486 

 --001,343 



- -001,454 



- -000,930 



- -001,125 



- -001,633 



4. 1 -0047 ^27fl l~ -000,648) ? f- -000,7951x1 

 + 1 0047 3276 + 6724 |_ . 001>125 | jj , 



or 



Hence 



R = + -000,1320, for r='80, 

 = + 000,1749, for r = -85. 

 d/N = -223,4275, for r = '80, 

 = 235,8233, for r = '85. 



Then interpolating linearly for d/N = '223,4670, we have 



395 



r = -80 + -05 x 



= -80016, 



124958 

 which is sufficiently close to the result '80013 of the equation method. 



The forward difference formula (e) gives a slightly worse result, namely r = '80021. 



Illustration (xv). Binocular Vision and Vision of Better Eye. (Boys.) 



Vision of Better Eye 



