iSixSigma

Thomas Subia

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  • #202492

    Thomas Subia
    Participant

    John,
    Here’s how you run Grubbs or Dixon’s outlier test in Minitab.

    Go to Stat, Outlier test,
    Under options choose the test you wish to do.
    Be careful when you choose a outlier test method.

    Minitab suggests that if you don’t know whether your data include outliers, use the Grubbs’ test.

    There are options for Dixon’s test or Grubb’s test. For more information on those tests go to:

    As always look at your data with a Box Plot or a Q-Q plot just to see what your distribution looks like.

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    #202491

    Thomas Subia
    Participant

    Let’s start with the following model:
    response = function of (A,B,C,D,AB,AC,AD,BC,BD,CD,ABC,ABD,BCD)
    If one did a stepwise regression model of all these variables, then one could see the AIC differences between models. It would be interesting to see if there was the model with (A,B,C,D, AB AD, ABC) had a lower AIC than the model with (A, B, C, D, AB, AD).
    In any event, you could use the stepwise regression model to determine which models were better than others in terms of AIC.
    One needs to be careful when using stepwise regression. If some of your variables are highly correlated then one may eliminate a variable which may not be wise in some cases.
    This technique may be useful for you!

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