I understand the concept, I know what the formula is, but who can tell me where the 1.41 multiplier came from?

Pardon my tardiness this week, as I had a major hard disk crash that I am still recovering from...

I'm not a statistical expert, so mine is a laymans answer. My official response is to recommend posting this in the Statistical Techniques and 6 Sigma page, as I think the statistical gurus can do it better justice. My other unofficial answer is that I think the inventor of the concept probably had a lot to do with it. I'm not well versed on those peoples names (Deming, Shewhart, and so forth).

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