iSixSigma

R Chart

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  • #43002

    Rich Conforti
    Member

    I have collected some variable data and I need to calculate my range of data using an R chart. When I run the test using Minitab, Minitab is not allowing me to enter my upper and lower specs. What test can I run and still be able to enter my upper and lower spec? I no my data is out of range just by looking at it but I need a chart to show my boss. Any help?

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    #136069

    Openball
    Participant

    I guess you have a misunderstanding of control charts.
    The control limits drawn on a control charts are different from your specifications. Specifications are your artificial requirements. However, in-control or out-of-control is not judged based on such outside requirements.
     
    For your specific requirement, you can input your desired control limits in Minitab (I am using release 14)  by: R chart->R-options. You can then tell Minitab the std.dev. of your process under “parameters”, and specify the location of control limits under tab “S Limits”.
     
     

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    #136083

    Zero_Cool
    Member

    Mr. Conforti,
    You can do this:
    Minitab> Stat> Control Chart> R… input there your data and your done with the graphical analysis.
    Why do you need specs in R chart anyway? Are you confused or something. You might wanna use Capability Analysis (Index)
    It is very hard to show and explain something to your boss if you don’t know what is it you wanted and what it is your doing. If you do such, it will also make your boss utterly confused.
    If you have variable data and specification (USL/LSL), use capability analysis to show process performance to your boss. Minitab can provide an excelent graphical presentation that you and your boss might take some time time to ponder. Who knows, he might might give you a pat in the back for this great work or it might be in reverse.
    Need to go. A lot of droids to fix. You might wanted to borrow R2D2 or C3PO for this purpose.
    Zero_Cool 
     
        

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