THE INTERCONNECTION OF TELEPHONE SYSTEMS 543 



one thousand will be lost. Evidently, 



gx + _v = 105, X + y = 30, x = 25, y = 5, P = .001 ; 

 from which, solving the first three equations simultaneously, we find g. 



O I 2 3 4 5 6 7 



TOTAL TRUNKS IN MULTIPLES OF (X + _y; 



Fig. 10— Graded multiple efficiency, x + y = 30. P = 0.01. 

 the number of subgroups, equal to 4. To enter the appropriate chart 



IX -\- y ... ,105 



X -^ y 

 The g = 4 curve at this abscissa of 3.5 gives us the gain over the 



(Fig. 14) we must determine the ratio ''" . ' , which equals-^ = 3.5. 



U 28 



O 12 



12 3 4 5 6. 



TOTAL TRUNKS IN MULTIPLES OF (x + y) 



Fig. 11 — Graded multiple efficiency, x + y = 40. P = 0.01. 



