26 MASS STUDIES IN BUILD. 



From these results the conclusion is drawn that since the variability 

 (standard deviation) of weight ;-s- chest-girth 2 is least, the square of 

 the chest-girth varies more closely with weight than either the first 

 or third power of chest-girth ; consequently the square of chest-girth 

 is the best measure of weight of the three. 



By hypothesis, the chest-girth in persons of the same build varies 

 very closely or exactly with stature; consequently we could substitute 



of" Q "f"11 T»fi 



in the foregoing ratios for chest its average equivalent, - — _ — , 



K 



in which K is nearly 2, more precisely 1.9. In any case it is thus 



clearly deducible that a better index of build is got by dividing weight 



by the square of stature than by its cube, as has been so often done. 



Accordingly, the ratio of weight to stature 2 has been adopted in this 



paper as the standard index of build. The correlation between this 



index of build and relative chest-girth is found by calculation to be 



about 0.45. 



In any scale of index of build it is, of course, desirable to use the 

 metric system. Unfortunately, most of our data are in English units, 

 so that our indices were first obtained by the use of these units. We 

 have in many cases transmuted the English into the equivalent metric 

 measures. We have, however, retained the original English index, 

 since a large portion of the more cultured part of the world uses that 

 system in daily life. A table to facilitate transmutation is also given 

 in the Appendix, table XVIII. To facilitate the determination of the 

 index of build when stature and weight (in English or metric units) 

 are known, table XVI has been prepared (pages 169, 170). 



To avoid decimals, the ratio, weight in pounds -4- (stature in 

 inches) 2 is multiplied in this book by 1.000; this gives a series of 

 ratios running from 20 to 60 and over. To avoid confusion with the 

 English system, the metric equivalents are taken as the ratio of 

 weight in grams -^ (stature in centimeters) 2 . This gives a series of 

 index numbers of the order 1.5 to 4.0; in this case, at least, one decimal 

 is always expressed. The small integral figure and the decimal at 

 once indicate that the index is from metric units. Since the index of 

 build has often been expressed as the ratio of weight to, respectively, 

 stature, stature 2 5 , and stature 3 , table XVII has been prepared to per- 

 mit these ratios to be transmuted into weight -f- stature 2 , English 

 system. 



CLASSIFICATION OF BUILD. 



For the purposes of analysis, it was found necessary to make a 

 small number of classes of build. To decide upon the limits of these 

 classes, a polygon of frequency of all indices of build was made, as 

 shown in figure 7. It appeared plain at the outset that it is desirable 



