. INSPECTION IN MANUFACTURING PLANT 41 



if it fails to meet requirements, usually warrants a strict AOQL. A rather 

 generous AOQL may be assigned to inspection features which are considered 

 relatively unimportant. In other cases the use of sampling may be defi- 

 nitely inadvisable due to the importance of the requirement from a func- 

 tional standpoint or from the standpoint of the possible effect of a failure 

 upon the safety or health of an individual. 



As a guide in the selection of the AOQL, the following table is given, 

 showing values that have been found to be satisfactory for the product 

 listed. These percentage values of AOQL represent per cent of articles 

 defective; if more than one defect is found on an article, the article is counted 

 as one defective. Here, as elsewhere throughout the paper, all figures relate 

 to number of defectives and per cent ot articles defective rather than num- 

 ber of defects. 



The process average is commonly determined by summarizing the results 

 of the first samples inspected during a representative period and may usually 

 be obtained if there has been a previous inspection with associated records. 

 In case suitable records are not available, an approximation may be made 

 on the basis of an examination of a number of random samples selected 

 from product of current manufacture. This will be a tentative figure and 

 may require revision when data accumulated from the operation of the 

 Double Sampling Plan are available. 



L3 Issuance of the Inspection Layout — Fig. 2 



After the AOQL value has been established, definite instructions in the 

 form of a Sampling Layout (See Fig. 2) should be provided for the use of the 

 inspector. The layout should contain a list of the inspection items for 

 which inspection is required. It should also contain a copy of the sampling 

 table selected, a description of the material to be inspected, AOQL value, 

 process average and other information which is of importance either in using 

 or in maintaining the Double Sampling Plan. 



* This is a process check for these requirements which is supplemented by another 

 sampling inspection after assembly. 



