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Production sequences

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  • #28916

    Joanne Heys
    Participant

    Could someone please tell me what is meant by the following question:
    How do you know the difference between computing sigma from a data set whose production sequence is known and from a data set whose production sequence is not known?
    Also: Please provide an example if you can.
    Thanks in advance,
    Joanne.
     
     

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    #72808

    Phil Whitman
    Participant

    Joanne:  I’m assuming that by “production sequence” you mean “process.”  In that you know one process versus the other.
    So, you have a data set of samples from one process you know versus another you don’t, and therefore data from several subgroups from two different processes.  Given the blindfold “taste test,”  how would you know which data came from which process unless there is some other information to which we’re no aware?  It doesn’t make sense to me and I’m interested in reading the answer.
    Sorry I couldn’t help you with that one.  I say take the person who wrote that question and punch them in the mouth.
    Good luck, just don’t bite their ear off, otherwise you’ll be making millions and won’t know what to do with yourself. 

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    #72810

    Joanne Heys
    Participant

    Hi Phil,
    Thank very much for your reply. As soon as I know the answer, I’ll let you know.
    By the way – the question came from Thomas Pyzdek – ‘The Great Six Sigma Consultant’.
    Thanks again,
    Joanne.

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    #72811

    Shree Phadnis
    Member

    Dear Joanne,
    When the manaufacturing sequence is known , you can have the data collected in Sub Groups or no subgroups.In either case depending on how the data is collected you can estimate the population standard deveation from the sub groups or the Range and use R bar/ d2  or Sbar/C4 depending on the no of subgroups for the estimation of standard deveation free from special causes, But when sequence of manufcturing is not known you use the conventional standard deveation formula (some times even multiplied by an unbiased estimator).In this method you estimate the population standard deveation which includes both common causes and special causes.For further understanding there are numerous posts on this site for PP,PPKCP&CPK.To put in short Cp and Cpk cannot be calculated without time sequence being known however Pp and PPk can be calculated.
    Shree Phadnis

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    #72812

    Joanne Heys
    Participant

    Shree
    Thank you very much for your help.
    Joanne.

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    #72821

    RR Kunes
    Member

    Good question.
    Sigma calculations are a function of DPMO not sequence. Perhaps they were referring to Rolled Thrtoughput Yield RTY. This is when you take the first pass yield at each step in an operation and multiply these values together to obtain a single yield value. Then convert that yield to a sigma value.
     

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