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Control chart for groups of data

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  • #50332

    Richard
    Member

    I have 6 lots of data from a process and would like to plot using IM-R chart or similar.  I was wondering is it possible to put all the data onto the same chart and have limiits calculated for each section (x6)? So I can show before improvement, during and after all on the same chart? Do I just need to use subscipts for each group and if so how do I then chart on 1 sheet?
     
    Thanks

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    #172975

    Kannan
    Participant

    Whats the harm in using different charts. It would look neat as well
     

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    #172979

    Bower Chiel
    Participant

    Hi Richard
    What software are you using?
    Bower Chiel
     
     

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    #172980

    Richard
    Member

    Hi Bower,
    Minitab, Yes sorry that was an after thought.
     
    Richard

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    #172983

    Bower Chiel
    Participant

    Hi Richard
    You can achieve what I think you require by having one column for your individual data values and another for the lot number: – 1, 2, 3, ….  .  Under I Chart Options the Stages tab enables you to define stages using the lot number column.
    Good Luck!
    Bower

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    #172984

    Kannan
    Participant

    Good one Bower

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    #172997

    Richard
    Member

    Hi Bower,
    Thanks for that. I had tried that and didn’t give em exactly what I was after? Its along the right line but I would like to disply it on a continuous  single chart with limits recalculated for each section in sequence? Perhaps you cannot do it but I’m sure I’ve seen it done somewhere. I’ll keep trying, any other ideas?
    Richard 

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    #172999

    Bower Chiel
    Participant

    Hi RichardIf you post an e-mail address I’ll send you some more details.Bower Chiel

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    #173069

    Saleem
    Member

    can u send me the details
     
    my id is [email protected]

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    #173070

    Venugopal G
    Member

    Hi Richard,
    Can U send me the e-mail ID so that I can post an example. If I understood correctly, U are looking for a single chart with both before and after situations and also the control limits have changed indicating the improvement and there is a shift in the mean.
    Regards,
    G. Venugopal
     

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    #173071

    Viswa
    Member

    Hi Richard!
    You will have one more Tab in the I-MR option called “Display”. Under it just tick the “display control limit/center line labels for all stages”. Click OK. u can see the means and comtrol limits at all stages.
     
    Regards
    Viswa

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    #173172

    Saherngu
    Participant

    I prefer using one chart showing the before and after with the computed ucl and lcl based on pre change.

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    #173180

    Richard
    Member

    Hi Venugopal / Bower
    My email address: [email protected]
    Thanks for your help
    Richard

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    #173182

    Ron
    Member

    You have described the requirement for the most powerful shewhart chart..the Xbar & R chart. It displays within and between process variaiton.
     

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    #173184

    Richard
    Member

    Hi Thanks everyone I’ve cracked it! it was as suggested by Bower the Stges under IMR Option tab. I must of had other items selected whilst rying to find the right solution that was confusing issues.
     
    Cheers

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    #173198

    Ron
    Member

    ricjard,
    6 groups of data is not sufficient to calculate fixed control limits. Typically a minimum of 25 to 30 sample lots of data is required statistically.

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