548 



BELL SYSTEM TECHNICAL JOURNAL 



assumptions without going through the burdensome process of accumulating 

 actual data in reliable volume and with useful frequency. The formula 



0.6 

 0.5 

 0.4 



5 0.05 



O 



E 0.04 



u 



e) 0.03 



7 8 9 



SIZE OF GROUP 



Fig. 5 — Average circuit delay on all calls expressed in terms of the holding time per circuit 



attempt. 



also provides a convenient means of checking the adequacy of the trunk 

 facilities in any unusual situations which may be observed from time to time. 



