QUALITY CONTROL CILIRTS 603 



ductlon data by applying some of the modern tools of the statistician. 

 The chart tells the manufacturer at a glance whether or not the product 

 has been controlled. Evidence of lack of control calls for immediate 

 attention, but there need be no time lost in looking for causes of varia- 

 tion in product when these variations are not large enough to indicate 

 lack of control. 



There is an obvious advantage in using all parts of the chart wherever 

 possible, because, as the illustration shows, one part may reveal trouble 

 even though some other parts do not. However, when the inspection 

 is made on the basis of attributes, the data will be available for the first 

 or percentage defective part of the chart only. 



