CHAPTER V. 
PERCENTILE GRADES OF WEIGHT, HEIGHT STANDING, HEIGHT SITTING, SPAN 
OF ARMS, GIRTH OF CHEST, LENGTH OF HEAD, WIDTH OF HEAD, HEIGHT OF 
FACE FROM ROOT OF NOSE TO POINT OF CHIN, WIDTH OF FACE, AND HEIGHT 
OF FACE FROM HAIR LINE TO POINT OF CHIN. 
The Percentile Grades of weight, height, etc., presented in 
Tables No. 17 to No. 28, inclusive, are represented graphically 
in Plates V to XXIV. By their aid, the percentile rank of 
an individual in respect of weight, span of arms or any physi- 
cal dimension included in the tables can be easily and quickly 
determined. Suppose, for example, the percentile rank of a 
boy, aged 11, weighing 32 kg. was desired. A horizontal line 
is drawn from 32 in the column of kilogrammes on the left of 
Plate V tothe curve of age 11, anda perpendicular is dropped 
from the point of intersection to the scale of percentile 
grades at the bottom of the plate. The perpendicular falls at 
60 per cent. Hence the bov is heavier than 60 per cent. of 
boys of his age and lighter than 40 per cent. 
Other facts are made plain by these curves. The increase 
at any percentile grade during one or more years is expressed 
by the distance between the curves at that grade. Thus, in 
Plate V, the gain in weight of the type-boy in the 15 per- 
centile grade during the years 6 to 11 inclusive is 9.3 kg., and 
the gain at the 85 percentile grade during the same year 13.0 
kg. The difference in size between large and small boys of 
the same age appears in the inclination of the curve to its 
axis, the slope being steepest in the years of quickest growth. 
And finally, the tendency of the greater number of individuals 
to approximate the middle value of their group is illustrated, 
the inclination of each curve being much less at the central 
part than at the ends, where the giants and the dwarfs are 
found. The principal service of such curves, however, is to 
determine percentile rank. 
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