2. Listen to the voice of the process
In order to spot abnormal variations that herald new trends or particular events, the theory of variations requires us to trace the natural limits of the process that produces our measurement or indicator.
We complete the chronological graph of observations with two limits that frame the average: the natural upper limit of the process (LSNP) and the natural lower limit of the process (LINP).
Variation theory tells us that :
any value within these limits is a normal value for the process or system observed by our indicator or measurement. Variations between different measurements can be considered as noise. There is no point in looking for specific causes for these variations, which are the result of the combination of multiple variations present in the process or system;
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Listen to the voice of the process
Spot abnormal variations
Bibliography
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Bibliography
Deming, Hors de la Crise , Éditions Economica
Shewhart, Les fondements de la maîtrise de la qualité , Éditions Economica
Wheeler, Understanding variations , Éditions SPC Press (Very didactic book, detailing concrete examples from the management of industrial companies. I have borrowed from this author the terms "natural process limits",...
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Association française Edwards Deming
Website of the Association Française Edwards Deming. This site offers a biography of Deming, as well as a series of free resources on Deming: a selection of articles, e-books and statistical software. You'll also find a French translation of Western Electric's Manual of Statistical Quality Control....
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