VARIATION 



19 



Having first obtained a number of measurements, 

 we proceed to classify the individuals by arranging 

 them in arbitrary groups. We may, for instance, 

 group together all men between five feet six and five 

 feet seven, between five feet seven and five feet eight, 

 and so on. It is desirable to make a considerable 

 number of groups, about ten or a dozen at least, and it 

 would obviously be a roundabout and unsatisfactory 

 method of describing variation merely to state the 

 percentage of individuals falling into each. 



Such continuous variabihty can be well expressed 



SQ 60 62 64- 66 66 70 72 7^ 76 78 

 Fig. 3. 



graphically. In order to do this we set ofi along a base 

 line a number of points to represent, say, the difierent 

 height classes into which we have separated a number 

 of men measured. We then measure vertically dis- 

 tances to represent the number of men falhng into each 

 class. 



In Fig. 3 this has been done with regard to measure- 

 ments of 8585 British men, the vertical fines repre- 

 senting difierences of one inch in stature, and the 

 horizontal fines hundreds of individuals. 



It vail be seen that the class which includes men 

 between 67 and 68 inches is the most numerous, there 

 being over 1300 individuals in it. The numbers in the 



B 



