REPORT OF THE ANTHROPOMETRIC COMMITTEE. 



247 



correspond respectively to :^'AB and to |"AB ; tlie lower and upper 

 deciles correspond to j^y AB and to ~^^ AB. It may be remarked that 

 the general shape of the cnrve will always resemble that shown in the 

 diagram, owing to the recognised statistical fact that medium values are 

 much more frequent than extreme ones, deviations from the mean value 

 becoming increasingly rare in a rapidly increasing ratio. 



In order to deduce approximately the above-mentioned curve from a 

 finite series of n observations, we divide AB into n equal spaces, and 

 erect an ordinate in the middle of each of a length proportionate to the 

 corresponding datum. The spaces will be defined by divisions that run 

 from 0° at A, to ii° at B, and therefore there will be ti + I of them. 

 The first ordinate will stand at 0°*5 of the graduated scale, the second at 

 1°'5, and so on, while the abscissae of the deciles, quartiles, and medians 

 will be at the following positions : to> h l» ?' > t^- The data are grouped 

 and tabulated as in columns A and B of the following example, which, 

 for the sake of simplicity in illustration, consists of only twelve obser- 

 vations. 



HEIGHT 

 IN 



INCHES 



54 



53 

 52 

 51 



50 



|o 2" 3° 4° 5° 6° 7° 8° 9° 10° 11° I 



B 



2° 



