Talk:Statistical process control

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This article was nominated for deletion on 2005-10-23. The result of the discussion was keep.

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Poor example

Final paragraph:

SPC indicates when an action should be taken in a process, but it also indicates when NO action should be taken. An example is a person who would like to maintain a constant body weight and takes weight measurements weekly. A person who does not understand SPC concepts might start dieting every time his or her weight increased, or eat more every time his or her weight decreased. This type of action could be harmful and possibly generate even more variation in body weight. SPC would account for normal weight variation and better indicate when the person is in fact gaining or losing weight."

fails to illustrate the use of SPC as an indicator of when it's appropriate to take no action. Could this example be improved? —Preceding unsigned comment added by 118.168.108.176 (talk) 08:19, 5 January 2009 (UTC)[reply]

What does the following extract mean ? This should be clarified or linked to supporting info.

The criticalness of the process can be defined by the westinghouse rules used.

The only way to reduce natural variation is through improvement to the process technology, see Nelson Funnel experiment. —Preceding unsigned comment added by 47.166.133.25 (talk) 18:07, 1 September 2009 (UTC)[reply]

The 'How to use SPC' section needs to outline that the data used to calculate mean and sigma must be from the process when it is known to be in control - generally it is not sufficient to take untested historical data. The process of establishing control can bring significant gain. —Preceding unsigned comment added by 94.193.145.39 (talk) 11:14, 2 February 2010 (UTC)[reply]