. The Bell System technical journal . ome correlationbetween the proportion of lost calls and the subgroup variation forhalf hours in any given unit interval of total load. The number ofcalls lost in these tests, however, is so small that plotting by half hoursthe large natural fluctuation due to other causes seems to completelymask any such small eftects which might be predicted. To further study the manner and amount of this subgroup variationin carried loads, similar calculations were performed by half-hour unitson the First Division of the tests (busy hours only) wherein the restric-tion o
. The Bell System technical journal . ome correlationbetween the proportion of lost calls and the subgroup variation forhalf hours in any given unit interval of total load. The number ofcalls lost in these tests, however, is so small that plotting by half hoursthe large natural fluctuation due to other causes seems to completelymask any such small eftects which might be predicted. To further study the manner and amount of this subgroup variationin carried loads, similar calculations were performed by half-hour unitson the First Division of the tests (busy hours only) wherein the restric-tion of unit range of average was not present. The results shown by 558 BELL SYSTEM TECHNICAL JOURNAL the heavy dots in Fig. 22, as might be expected, give sHghtly highervalues of variation for the non-restricted load values ^t gx -\- y = 36and 52 trunks than for the restricted cases belonging to the seconddivision of the tests. The remarkable point here, however, is thatthe phenomenon for the ranges studied exhibits practically a straight. 32 36 40 44 48 NUMBER OF TRUNKS IN GRADED GROUP Fig. 22—Change in subgroup load variation with number of trunks in group. line relationship between variation of subgroup loads and the numberof trunks per subgroup, a difference of four in total trunks meaningan increase of one in each subgroup. An added variation for thelarger number of trunks seems only natural, however, since as thesubgroup size is increased part of the fluctuations previously borneby the commons is transferred to each subgroup itself. That thisnatural increase in subgroup variability does not affect the grade ofservice of the larger groups for busy hour measurements seems to beamply demonstrated by the consistency of the Half Gain formulain fitting the observed number of trunks in Fig. 16. We conclude,then, that a formula based on the third assumption (equality of sub-group loads), is considerably at variance with actual results; bymodifying this assumption, to approximate loa
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