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How to Calculate Standard Deviation Within Value Using Excel

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  • #254463

    kittinadhazi
    Participant

    Hi guys,
    I write my thesis sixsigma, and I need some help.
    I would like to calculate standard deviation WITHIN value in excel ( without any program e.g. SPC or sometthing like that), I have 60 datapoints and I havent got subgroups. I know I shouldn’t calculate within value, if I havent got subgroups, but ( my friend has got Minitab) and I put my values in there and minitab gave standard deviation within value. And it’s really important, because minitab uses this results for calculate CPK value.

    So my question is, how can I do it in Excel? what is the method of Minitab? I found an article in their page, but isnt help me. Really important, that I know how it works. ( because I will write my thesis)

    I will be grateful, thank you so much :)

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    #254479

    Robert Butler
    Participant

    My guess would be your friend did something wrong in Minitab. If you don’t have subgroups then there is no within to use for calculations. Is there any chance the standard deviation it did compute was either just the sample standard deviation of all 60 points or the standard deviation of the mean of the 60 data points?

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    #254554

    Daniel Alfano
    Participant

    I had the same question some years ago and found the answer in one Minitab post. Please look at the attached file with the Excel formulas to calculate the “with in” stdev, same as Minitab.

    Attachments:
    1. capabilityhw-resuelto.xls
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