976 



THE BELL SYSTEM TECHNICAL JOURNAL, JULY 1953 



of the process average results in the use of two sets of control limit lines 

 for averages in place of the one used for conventional methods. These 

 consist of : 



(1) A relatively narrow band equal to N zk O.IA {N :h }i(r), desig- 

 nated in the general specification as "Z>" limits. 



(2) The normal 3-sigma limits for averages of samples of 5 units 



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J»0-H (1-51) 



CONTROL SHEET 



Q-ZJ-SH, 



IS07F INDUCTOR 



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iNOucraNce. 



CHARACTERISTIC 



UmT OF MEASUREMEHT M/rHfiH£NHIP< fJHaUf ^J2 ■ Q I WSP. METHOD 



SPECIflCATIOH iiuiTS;-MIN. 2.1.7 M AX. 2.S. I INSPECTOR _ 



.MANUFACTURED BY 



.MACHINE HO._jr GROUP HO^ 



OPERATOR NO. 



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Fig. 4 — A typical control chart (1507E inductor). 



