A METHOD OF RATING MANUFACTURED PRODUCT 



363 



(2) The product which passes this inspection is subsequently examined 

 on a sampHng basis by a check inspector who looks for the same 

 defects. 



The data obtained by the screening inspection provide a measure of 

 the quality submitted by the Operating Department. The check 

 inspection data give a picture of the quality of the finished product 

 placed in stock. The rating chart is shown in Fig. 8. In a case of 

 this sort where identical product is handled by two successive inspec- 

 tion groups, it is advantageous to show both rates on the same scale. 

 In this particular instance a rate of corresponds to the base period 



Fig. 8 — Rate showing quality of a product before and after a screening inspection 



quality of the product submitted to the check inspector. The control 

 limits for the lower rate are drawn above and below the expected level 

 of quality for product submitted to the first group of inspectors and 

 both sets of limits are based on a probability of .95. 



The results of the screening inspection can be used directly for con- 

 trolling the work of the Operating Department. For this purpose it 

 has been found valuable to prepare weekly rates with control limits 

 based on a slightly lower probability value than that used for monthly 

 rates. When the defects can be readily classified into two or more 

 major groups, such as defects for electrical requirements, defects for 



