A Method of Rating Manufactured Product 



By H. F. DODGE 



Synopsis: This paper outlines a method of rating manufactured product. 

 In the particular form here described, the rate has been found very useful 

 for measuring the quality of communication equipment and materials 

 entering the plant of the Bell System. While the primary object is control 

 of quality of finished product, it is proving useful for measuring the work- 

 manship of individual operators and groups of operators engaged in similar 

 production work. Particular attention is directed to the statistical aspects 

 of the rate to show how it can assist in controlling quality. 



C"^ IVEN a product whose quality is dependent on a number of 

 X diverse characteristics, the following questions and others similar 

 to them frequently require answers. Has quality been satisfactorily 

 controlled? Is there any general trend in quality either upward or 

 downward? How does current quality compare with that of a year 

 ago? 



These are questions of importance to the manufacturer. Qualitative 

 answers can often be given on the basis of general knowledge by those 

 familiar with the details of manufacturing performance but such an- 

 swers tend to be inaccurate or biased. What is often wanted is some 

 statistical index based on quantitative data, a figure which balances 

 the favorable features against the unfavorable to give an overall 

 picture of quality on the average. 



To get such a picture does not in general require special data. The 

 detailed data obtained in the course of routine inspection, while often 

 used only for the immediate purpose of determining the satisfactoriness 

 of individual lots of product, are just what is needed for the present 

 purposes. These inspections are critical examinations of the features 

 that are essential to proper operation of the product in service. Hence 

 the results are a measure of quality. There are of course many 

 possible ways of classifying and combining this quantitative informa- 

 tion, some of which are more efficient than others. The problem is to 

 set up a method of handling the data in a way which will paint as clear 

 a picture as possible of the overall quality. 



The rate here described has been found very useful for measuring 

 the quality of communication equipment and materials entering the 

 plant of the Bell System. ^ It recognizes and takes account of the rela- 

 tive seriousness of different types of defects found in the course of 



1 This method of rating is being used extensively by the Manufacturing Depart- 

 ment of the Western Electric Company where some of the features outlined in this 

 paper originated. 



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