Solved: Re: Within standard deviation formula

MichaH · Sep 4, 2024 06:27 AM

Hi, can anyone help me ideally in excel to show me how Within sigma was calculated, I am able to get only Overall

Thank you

statman · Sep 4, 2024 11:19 AM

Actually, the picture you posted is using a moving range to estimate the within standard deviation. The MR uses a surrogate subgroup size of 2 (previous-current). You will need the average MR.

estimated standard deviation = MR-bar/d2

"All models are wrong, some are useful" G.E.P. Box

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MRB3855 · Sep 4, 2024 06:43 AM

Hi @MichaH : Hopefully this answers your question.

https://community.jmp.com/t5/Discussions/Process-capability-within-sigma-estimation-for-different-nu....

MichaH · Sep 4, 2024 08:17 AM

Hi,

I have subgroup size of 1, so not cleaver much...

statman · Sep 4, 2024 11:19 AM

Actually, the picture you posted is using a moving range to estimate the within standard deviation. The MR uses a surrogate subgroup size of 2 (previous-current). You will need the average MR.

estimated standard deviation = MR-bar/d2

"All models are wrong, some are useful" G.E.P. Box

MichaH · Sep 4, 2024 11:31 AM

Hi,

stunning evening. Finally I got it and able to replicate by manual calculation. You saved my day. Thank you a lot.

Michal

txnelson · Sep 4, 2024 07:23 AM

Why do you need to do this in Excel?

Jim

MichaH · Sep 4, 2024 08:18 AM

Hi Jim,

because I need to understand the mechanism behind to explain others