VIL.—THE FREQUENCY-DISTRIBUTION. : 
TABLE IV. Showing the Annual Value and Number of Dwelling-houses in 
Great Britain assessed to Inhabited House Duty in 1885-6, (Cited from 
Jour, Roy. Stat. Soc., vol. 1., 1887, p. 610.) 
Annual Value in #5, Number AY 
nnua alue in S, of Houses. al 
£20 and under £30 306,408 306,408 
30 5s 40 182,972 | 182,972 
40 5 50 105.407 | 105,407 
gol 60 63,096 63,096 
60 4 80 71,436 35,718 
80 i 100 52,365 16.182 
100 at 150 41,336 8 7a7 
150 5 300 26,732 . 
300 " 500 6,198 
500 ” 1000 2,008 
1000 and upwards Lh 
Total number of houses 838.6: ° 
reduced to a common interval as basis, e.g. £10, by dividing the 
fifth and sixth numbers by 2, the seventh by 5, the eighth by 15, 
and so on. This gives the mean frequencies per £10 interval 
tabulated in the third column of Table IV. The reduction is, 
however, impossible in the case of the last class, for we are only 
told the number of houses of £1000 annual value and upwards : 
the magnitude of the class is indefinite. Such an indefinite class 
is in many respects a great inconvenience, and should always be 
avoided in work not subject to the necessary limitations of 
official publications. 
The general rule that intervals should be equal must not be 
held to bar the analysis by smaller equal intervals of some 
portion of the range over which the frequency varies very 
rapidly. In Table XII, p. 98, for example, giving the numbers 
of deaths from diphtheria at successive ages, a five-year interval 
might be substituted with advantage for the irregular intervals 
after the fifth year of age, but it would still be desirable to give 
the numbers of deaths in each year for the first five years, so as 
to bring out the rapid rise to the maximum in the fourth year 
of life. 
11. When the table has been completed, it is often convenient 
to represent the frequency-distribution by means of a diagram 
which conveys the general run of the observations to the eye 
better than a column of figures. The following short table, 
83