THEORIES FOR TOLL TRAFFIC ENGINEERING IN THE U. S. A. 



479 



of siniiiltaneoiis calls. The agreement again is reasonably good, in spite 

 of the considerable disparity in variances. 



The overflow from XBT and the load which by-passed it, as well as 

 some other miscellaneous parcels of traffic, were now combined for final 

 offer to the Suburban Tandem group of 17 trunks. The comparison of 

 parameters here is again available in Table XI. On Fig. 35 are shown 

 the observed and calculated distributions of simultaneous calls for the 

 load offered to the ST trunks. The agreement is once again seen to be 

 very satisfactory. 



We now estimate the loss from the ST trunks for comparison with the 

 actual 'proportion of calls which failed to find an idle path, and finally 



Table XI — Load Offered to Suburban Tandem 



Average. . 

 Variance . 



Theory 



15.38 

 42.06 



Observed 



14.52 

 48.53 



THEORY OBSD 



f(n) 



P^n 



10 20 30 40 



n = NUMBER OF SIMULTANEOUS CALLS 



10 20 30 40 



n^NUMBER OF SIMULTANEOUS CALLS 



50 



Fig. 35 — Distribution of load offered to suburban tandem trunks; negative 

 linomial theory versus throwdown observations. 



