( JH i'KOCKEDINOS OF THE ANATOMICAL AND ANTII KOl'OLOGICA I, 



called the I'rolmlilc Error. It means that if a measurement is made 

 of a person taken at random from the whole population, the chances 

 of this measurement being a greater or less distance from the mean 

 than the probable error are equal. 



The probable error = standard deviation x -(37449. 



The mathematical theory of the law of error is too extensive to 

 be expounded in this paper. I shall content myself therefore by 

 giving the formula 1 for finding the probable errors of the leading 

 anthropometric values : 



'67449 

 Probable error of a mean = - or. 



^ 



Take for example the mean head length of the 364 persons 

 already found to be 19:5 '0835. 



Probable error = - ~ x 5-642 

 v/364 



= -1993. 

 The mean length should therefore be written 193*9835 *1993. 



Probable eiror of standard deviation = , - o-. 



N/2N 



The general formula for finding the probable error of any /*. 



67449 _ 

 Probable error in = - ./ _ U 2 



VN 



The mean and (standard deviation)- are ^ and /t. 2 , so that their 

 probable errors can be deduced from the general formulae. 



The probable errors of all values calculated from the statistics of 

 samples should invariably be calculated and stated as after the 

 value, otherwise we are liable to deduce erroneous conclusions from 

 our results. 



I have not been able to give more than a very general exposition 

 of the new method of treating anthropometric statistics as the subject 

 is very extensive and would require a course of lectures rather than 

 a single paper to give you a real working knowledge of it. What 

 I have said may, however, stimulate some of you to pursue the 

 subject further, 



