XXVIII] 



Introduction 



xlix 



Write h„ = c^, b, = lOco, b,, = 100c.,, 63 = IOOOC3. 



Then our equations are 



•23650 = 6„ X -31000 +b,x -24800, 



1-83345 = 6, X -24800 + 63 x -35662, 



•45603 = 6„ X -24800 +b^x -35662, 



2-48808 = 61 X -35662 + 63 x -60966 ; 



giving &„ = - -58626, .-. c„ = - -58626, 



b, = 1-686453, c, = -016,8645, 



6, = 9-59613, Ci = -959,613, 



63 = - 1-532,144, C3 = - -001,532,144, 



and the required cubic is 



2/ = - -58626 + -959,613a; + -016,8645ar= - -001,532,144a;^. 



45 



40- 



35 



25 





15 



20 



25 30 35 



Age of Bride. 



40 



45 



The graph of the cubic and the observations are given in the accompanying 

 diagram. If A"^ and 1' be the actual ages of bride and groom, then 



Y = 61-30457 - 4-344,941Z + -157,0553Z^ - -001,53214X^ 



For higher parabolic curves fitted to the same data, see Biometnka, Vol. II. 

 pp. 21—22. 



B. g 



