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NON NORMAL DATA

Six Sigma – iSixSigma Forums Old Forums General NON NORMAL DATA

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  • #33430

    ASAD
    Participant

    Hi:
    Any one can help me how I handle the non normal  data for Six Sigma calculation such as capability or sigm level. As we know ”
    One of the technical aspect of criticism that the normal distribution is just a model and it does not represent most of the process. Other realistic process model such as log normal, student’s t etc. will make the case for Six  Sigma  even more emphatically because they all will predict a much larger probability of producing a product out side the specifications. Regardless process stability is perhaps more important than distribution. ”
    Thank you for your cooperation
    Cheers !! !
    ASAD
     

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    #90389

    Gangadhar (Ganges) Bhardwaj
    Participant

    If data is Non Normal and Continuous we should use Product Report in Minitab (L1 Spreadsheet)
    Calculate Defects per Unit,  Total Oppurtunites, Defects per Oppurtunity (Probablity of defect) ane DPMO
    Then use the Z Table to convert DPMO to Z Value and add Z shift to calculate Z bench (Long Term Capability)

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    #90448

    Tony Burns
    Member

    Normality cannot be assumed for any distribution. There are a variety of ways to estimate dispersion, described in detail in Chapter 3 “Advanced Topics in SPC”. Looking at the extreme tail of a distribution is not one of the methods listed. The tail is a very poor indicator of the shape of the dog.
    Dr Tony Burns
    [email protected]

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    #90450

    ASAD
    Participant

    Dear Dr Tony Burns:
    Thank you for your valuable suggestion and let me know the writer of the book  chapter 3 “Advanced Topics in SPC”. So I can go further to the topics.
    With best regards
    ASAD

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    #90451

    Tony Burns
    Member

    The author is Dr Donald Wheeler. SPC Press.
    It’s very thorough and great reading.
    Dr Tony Burns
    [email protected]

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