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XbarR Question

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  • #51264

    newbie
    Participant

    If I have an XbarR indicating an increase in ‘within subgroup’ variation on the R Chart with a pattern of reduced ‘between subgroup’ variability on the Xbar Chart, how is this explained (generally speaking)….??

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    #177416

    Ron
    Member

    The R portion of the chart is made from the range data of the sample (i.e. the difference between the highest and lowest reading) the bewteen subgroup  is the average reading of the samples. If you have a extremely high range this could average out to a reasonably low number.
    Interrogate the data and see what it looks like.
    Sounds like the procesds is out of control. Or the measuirng system
     
     

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    #177458

    Jonathon Andell
    Participant

    Agreed. I also would look into the rational subgrouping scheme, to see if the samples within subgroups truly are random. It may be a flawed sampling approach.
    Sometimes, plotting every data point on a I chart may reveal systematic patterns that suggest sampling problems.

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