VII.—MEASURES OF DISPERSION, ETC. 2 
CALCULATION OF THE STANDARD DEVIATION: Erample ii. — Calculation of 
the Standard Deviation of the Percentages of the Population in receipt of 
Relief, in addition to the Mean, from the figures of Table VIII. of 
Chap. VI. (Cf. the work for the mean alone, p. 111.) 
(1) (?) (3) (4) (5) 
Percentage Deviation 
in receipt frengensy. from Value 4. Prodacs, Pe, 
of Relief, , ¢. 2% : 
1 18 - 5 90 450 
1'5 48 - 4 192 | 768 
2 72 - 3 216 648 
2-5 89 - 2 178 356 
3 100 = J 100 100 
3-5 90 -776 — 
4 75 75 
45 120 240 
120 360 
5 84 336 
55 275 
vd 30 180 
; 49 
Po ; 64 
2H J 100 
Total +509 411] 
From previous work, p. 111, M- 4 =d= 04225 class-intervals, 
3(f%) 4001 _ 
= =55=6 3307. 
o's l= 63307 - (4225)? 
=6'1522. 
«*. o =248 intervals =1'24 per cent. 
To illustrate again the value of the standard deviation for 
purposes of comparison, figures are given below showing the 
means and standard deviations of similar distributions for a series 
of years from 1850. It will be seen that not only did the mean 
decrease during the period, but the standard deviation decreased 
to an equally marked extent, having been halved between 
1850 and 1891 ; the average was lowered, and at the same time 
the percentages of the population in receipt of relief clustered 
much more closely round the lower average. 
139 
¢