42 NATURAL INHERITANCE. [CHAP. 



It must be understood that M, like the Mean or the 

 Average, is almost always an interpolated value, corre- 

 sponding to no real measure. If the observations were 

 infinitely numerous its position would not differ more 

 than infinitesimally from that of some one of them ; 

 even in a series of one or two hundred in number, the 

 difference is insignificant. 



Now let us make our Scheme answer another question. 

 Suppose we want to know the percentage of men in the 

 group of which we have been speaking, whose Strength 

 lies between any two specified limits, as between 74 Ibs. 

 and 64 Ibs. We draw horizontal lines (Fig. 4) from 

 points on the side scale corresponding to either limit, 

 and drop perpendiculars upon the base, from the points 

 where those lines meet the curve. Then the number of 

 Grades in the intercept is the answer. The Fig. shows 

 that the number in the present case is 30 ; therefore 

 30 per cent, of the group have Strengths of Pull ranging 

 between 74 and 64 Ibs. 



We learn how to transmute female measures of any 

 characteristic into male ones, by comparing their respec- 

 tive schemes, and devising a formula that will change 

 the one into the other. In the case of Stature, the 

 simple multiple of TO 8 was found to do this with 

 sufficient precision. 



If we wish to compare the average Strengths of two 

 different groups of persons,' say one consisting of men 

 and the other of women, we have simply to compare 

 the values at the 50th Grades in the two schemes. For 

 even if the Medians differ considerably from the Means, 



