A METHOD OF GRAPHICAL ANALYSIS 



97 



the average as shown on Figs. 12 and 13. For this data, it is noted 

 that, on an absolute message use interval basis, the greater the average 

 the greater the abscissa of the peak value. However, with an increase 

 in the average, the abscissa of the peak interval on an absolute basis 



1= 



£* 

 -< 



<o 



Oo 



400 600 800 1000 1200 1400 1600 1800 2000 2200 

 AVERAGE MONTHLY MESSAGE USE 



Fig. 12 — Determination of Normal Peaks 



200 



400 



600 800 1000 1200 1400 1600 1800 2000 2200 

 AVERAGE MONTHLY MESSAGE USE 

 Fig. 13 — Determination of Normal Heights of Peaks 



does not increase as rapidly as does the average, because large users 

 increase their usage relatively more than small users. Therefore, 

 when the intervals are plotted in terms of per cent, of the average, 

 it will be found that the greater the average the less the abscissa of 

 the peak. For the same reasons, the peak interval expressed as per 

 cent, of the average becomes relatively wider as the average increases, 

 and the height of the peak increases as illustrated on Fig. 13. With 



