A. O. POWYS 
243 
TABLE XI. 
Table of Regression For^mulce. 
?/ = Duration of Life; .r = Size of Family. 
(1) Life after 60 years of age, Mothers of 0 to 6 children, .?/= 9-6209 + -18187.*- 
(2) 
(3) 
(4) 
„ „ „ „ 6 to 17 „ y= 11-1936 -•14782.r 
75 „ „ „ 0 to 6 „ 2/= 2-1903 + -0584437 
„ „ „ „ 6 to 17 „ y= 3-01 70 --09788.1;. 
Origin at 0 children. Unit of x=l child. 
Cubic parabolas were also determined for these two series, and were found 
to be — the origin of both curves being at S'o children — 
For life after 60 years of age 
y = 10-465864 - 099753 x - -033096 x- - -000352 x". 
For life after 75 years of age 
y= 2-24.5851 --089609 -007900 + -000422^^3. 
The theoretical maxima were found to be at 6-955 and 5 268 children respectively. 
The statistics, regression straight lines and curves are plotted on Fig. 4. 
Fig. 4. Number of Offspring and Average Duration of Life of Mothers surviving Age 46. 
A, Beyond 60 years of Age. 
75 
s 
— ^ 
'a 
J 
\ 
4 
B 
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 
Size of Family. 
Equations to Kegression Straight Lines : 
aa', y= 9-6'209 + -18187^; ] 
66', 2/ = 11-1936 --14782X I Origin at 0 children. 
dd', y= 2-1903 + -05844j; [ Unit of x = l child. 
ee', y= 3-0170 - -09788x ) 
Equations to Cubic Parabolas : 
cc', ?/ = 10-465864- -0997530: - -033096a:2 - -000352:c3 } Origin at 8-5 children. 
ff , y= 2-245851 - -089609.r - -0079000-2+ -000422.t3 ( Unit of a: = 1 child. 
31—2 
