THE BELL SYSTEM TECHNICAL JOURNAL, JULY 1953 



the product within the limits implied by the control charts is left to the 

 initiative of personnel administering the application of the method. 



The records are based on measurements on samples of 5 units each 

 selected at random prior to the regular inspection of individual units for 

 conformance. The number of such samples should be adequate to provide 

 a control chart record of the quality of the product. 



In all of the methods described except the one requiring records only, 

 the final product is packaged in groups of 5 units for shipment. When an 

 order calls for a quantity other than an integral multiple of 5, the frac- 

 tional part of the group shall consist of units randomly selected from a 

 group which has been previously packaged. 



3.0 Factory Application 



3.1 general 



The Distribution Requirements are being applied to 91 components 

 consisting of 31 different codes of product used in the L3 carrier repeat- 

 ers. In addition, Record methods are applied to 66 characteristics of the 

 line and office amplifiers. 



The components involved are identified in Table II. 



These products require the maintenance of over 100 control charts in 

 the factory in a form suitable for reproduction since engineering review 

 of the results is necessary for adjustment of limits. Many of the charts 

 are prepared and handled by factory personnel who required and re- 

 ceived training in order to provide assurance of accurate results. Com- 

 prehensive instructions were prepared in order to assist in this training. 



Fig, 6 — A three-cell pattern superimposed on a frequency distribution of 

 individual units of product when the average is allowed to vary zt}i<r. 



