Single Sampling and Double Inspection Tables

C O N S I D E R A B L E a m o u n t of a t t e n t i o n has been given to the application of statistical methods to problems of inspection with emphasis on means for securing certain definite a d v a n t a g e s such as reduction in t h e cost of inspection, reduction in the cost of production by minimizing rejections, and the a t t a i n m e n t of uniform quality of m a n u f a c t u r e d products. 1 - 2 - 3>4 This paper presents four sets of sampling inspection tables t h a t h a v e contributed in a notable way to i m p o r t a n t reductions in such costs a n d to substantial improvements in control of quality for m a n y characteristics of products used in t h e Bell System. W h e t h e r sampling m a y be employed to a d v a n t a g e in place of 100% inspection usually depends, of course, on the purpose for which inspection is made. T h e sampling tables here presented provide definite procedures for conducting inspections t h a t have certain immediate purposes which are described in some detail. T h r o u g h their provision for instituting a "screening" inspection whenever quality falls below an acceptable level, t h e procedures have been found in practice to enforce a program of controlling quality in process as the alternative to high inspection costs. G E N E R A L F I E L D OF APPLICATION