\\l 



I'nhli-K for 



nmf li!<nn< tr 



[I 



the origin being the moan. Table I. gives the value of x/tr for each thousandth 

 of the area of this curve, each ' pcrmillc ' reckoned from left to right, 



In enterinj; tin- table we enter from the left-hand column ami toji row if the 

 ]ietmille be less than 500. For example, if the frequency below a particular value 

 were .'is" per thousand, the corresponding deviate would be 0*2871, the number 

 placet! at the intersection of the '38 row from left and '007 column from top. 

 The negative sign is always to be given when reading permilles In-low 500, 

 because the deviate will be in defect of the mean, supposing increasing variun - 

 to be plotted as usual from left to right. 



On the other hand if the permille be greater than 500 we enter the table from 

 the right-hand column and bottom row. For example, if the permille be 74-8, the 

 deviate is + 0'6682, the number placed at the intersection of the '74 row fmni 

 right and '008 column from bottom of the table. The plus sign must be given, as 

 the deviation is in excess of the mean, if the convention as to plotting variables 

 has been observed. 



Illustration: The following observations were made on the nature of the 

 degree taken by 1011 Cambridge undergraduates measured at the Anthropological 

 Society's Laboratory : 



Poll 



Third Class 



4S7 

 189 



Second Class 

 First Class 



182 

 153 



Find the deviates of these on a normal or Gaussian scale. 



The sums from the lowest to each class top are 487, 676, 858 and 1011 

 respectively. If we term with Francis Galtou the one man in a thousand of 

 surpassing intelligence or special ability a "genius," we have on multiplying by 

 0009891197 the reciprocal of 1011, the series for entering Table I. Thus we 

 find: 



II. !:' : 





(481) 

 (-482) 



A 

 Ax -7 



Supposing with Pearson* that 100 units of intelligence ("mentaces") separate 

 the lowest man of the First Class from the highest man of the Poll, we have 

 + r0309 ( '0458) = 100/tr, where a is the standard deviation of intelligence. 

 Thus ff = 100/1 '0767 = 92'88 mentaces. Hence we conclude that the range of 

 Third Class men is from - 4'25 (i.e. 92'88 x (- -0458)) below to + 4>0'50 



Hiumttrikti, Vol. V. p. 100. 



