VARIATION AM) DITY 7 



tween the frequency of a nation and the* 



amount of is d-\iatioi, from tin* mean stature of tin* 



i>. Among the measur of 2,600 men, taken at 



random . a* they come ami withoi. ..iiM-iou* 



effort t.. ided only tin- tall or the short), tl 1 of 



s in.: 12 of 5 i 1 about 1 



r. t't. 4 in.; that is, c<jual numbers at equal distances : 

 tli- mean of 5 This illustrates that when tin- 



frequency and the magnitude of the variations are 

 regi> "\v what is called the normal mrve of 



frequ This can he illustrated moiv -lrarl 



eren. inir table of tli< I s in .M-ntm 



11 HI t.-n and Jf \ear old American school hoys. 1 



Between 109 and 113 centimeters tall. 2 boys. 



When this mat. rial is plotted in graphical form the 

 di-trihuiion of stature is as ted in figure 1, 



lettinir the distance of each hori/.ontal line from the 

 base stand for the number of boys. Now if we 

 to draw a smooth curve through the tops of the columns 

 we should have a bell-shaped curve of the type shown in 

 figure 2. This illustrates graphically what we n 



t Thomdikr, E. L. /*<*iri<*iia/ify, p. 8. 



