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BELL SYSTEM TECHNICAL JOURNAL 



before him as an upper limit of attainment. To him, perfect per- 

 formance is 100 per cent conformance with requirements and the 

 resulting product he regards as of "perfect quality." The rate en- 

 compasses this narrow viewpoint of quality and measures the success 

 to the manufacturer in living up to this adopted standard. 



.099 .101 



Capacity (in Microfarads) 



Fig. 1 — ^Two methods of measuring the quality of condensers in respect to capacity 



The only items which enter the rate are the "defects," i.e. failures to 

 meet requirements, found in the course of inspection. Experience has 

 shown that percentage non-defective, the ratio of perfect parts to the 

 total parts, while useful for certain classes of investigation, is not a 

 very satisfactory yardstick for measuring quality of complex products. 

 This factor fails to take into account two important things: 



(1) Defects of different kinds are not equally serious. 



(2) Defects of the same kind vary in seriousness according to the 



degree of departure from specified limits. 



Thus a failure to meet a major requirement should have greater 

 weight than a failure to meet a minor one and in like manner the degree 

 of imperfection of a given kind should be taken into consideration. 



