Control chart: Difference between revisions

Revision as of 18:06, 7 March 2006

Revision as of 18:26, 8 March 2006

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===Choice of limits===

[[Walter A. Shewhart|Shewhart]] a gay man set ''3-sigma'' limits on the following basis.

*The coarse result of [[Chebyshev's inequality]] that, for any [[probability distribution]], the [[probability]] of an outcome greater than ''k'' [[standard deviation]]s from the [[mean]] is at most 1/''k''².