iSixSigma

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  • #30769

    Sah
    Member

    I have two quick questions, if someone could help, it would be greatly appreciated. I have a dataset that I need to apply some statistical measurement tools with
    What is the best tool to yield a prediction equation for my factors, would it be R&R or the Anderson-Darling?
    Also what would be the most beneficial test if I was testing for a difference in central tendency between various variables?
    Please advise, thanks!
    Student
     
     

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    #80605

    Aravena
    Participant

    Student,
    on question (1) my answer is neither.  Regression or DOE are your best bets for a prediction equation.
    on (2) “most beneficial” test is subjective…I would vote for Anova.
    pablo

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    #80610

    Sah
    Member

    Someone at the office suggested the Levene’s Test to test for a difference in central tendencies does someone have a clear definition for this test?

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    #80611

    Fernie
    Participant

    Student:
    I agree with Pablo on number 1, Regression analysis or DOE will help you obtain your equation.
    On question number 2, I disagree just because it depends in the nature of your data. If your data shows a Normal behavior then you can use one way anova or a 2 sample T test  to compare means for both groups of data (assuming you have 2 groups). If the data is Not normal, then you want to test the medians by using a non parametric test such as Mann-Whitney or Kruskall-Wallis.
    The Levene test is used to test for differences in the standard deviation of non-normal data sets.
    Hope this helps,
    Fernie

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    #80616

    Mike Carnell
    Participant

    Fernie,
    I agree with your post. Small point – Levenes tests variances.

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    #80617

    Mike Carnell
    Participant

    Actually if you are using Minitab you will get Bartletts and Levenes at the same time. You need to understand if you are dealing with normal or non normal data to know which to use.

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    #94659

    Kat
    Participant

    Mike –
    Just a couple of follow up questions to your response below.  As you indicated, Minitab does produce Bartlett and Levene at the same time.  If you do not know the distribution of the data or the data is non-normal, it is suggested to use Levene’s test. 
    Have you ever encountered a situation in Minitab where Bartlett’s test is less than .05 and Levene’s is greater than .05?  If so, what would you recommend as a next step?
    Thanks.

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