12.2. EWMA
12.2.1. EWMA charts
12.2.1.1. SPC TECHNIQUES FOR AUTOMATED MANUFACTURING
Many people erroneously believe that statistics are not needed when automated manufacturing processes are involved. Since we have measurements from every unit produced, they reason, sampling methods are inappropriate. We will simply correct the process when the characteristic is not on target.
This attitude reflects a fundamental misunderstanding of the relationship between a process and the output of a process. It also shows a lack of appreciation for the intrinsic variability of processes and of measurements. The fact is, even if you have a "complete" data record of every feature of every part produced, you still have only a sample of the output of the process. ...
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