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Interpreting Kruskal Wallis results

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  • July 9, 2008 at 1:16 am #50508

    Sorour
    ★ 10 Years ★
    Participant

    Hi all.
    Currently running the above test, adn have returned results where p=0.078, yet the Z-score of one of my factors is greater than 2 (2.24).
    To me, this suggests that the results are conflicting.
    Should my null hypothesis be rejected?
    Thanks,
    P

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    July 9, 2008 at 1:28 am #173654

    Michael Mead
    ★ 10 Years ★
    Participant

    The test statistic is actually Chi-squared didtributed. With 6 degrees of freedom the Chi-square score of 2.20 gives a p-value of 0.10.
    Good luck.

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    July 9, 2008 at 1:32 am #173655

    Sorour
    ★ 10 Years ★
    Participant

    Greeting Michael.
    I’m afraid I don’t understand that answer.
    Could you explain?
    Regards,
    P

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    July 9, 2008 at 1:48 am #173656

    Michael Mead
    ★ 10 Years ★
    Participant

    Hello Paul.
    Although I don’t use Minitab, I have seen the report for a Kruskal-Wallis H test and there is nothing on it about a “z-score”.
    This is a non-parametric ranking test to determine if 2 or more samples are from the same distribution. A p-value of .05 is usually used.  I don’t know exactly what you are trying to do with this test, so I can’t elaborate more. What I said before is a generalization.
    I guess at this point, neither of us know wht the other is talking about.

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    July 23, 2008 at 1:42 pm #174075

    Remi
    ★ 10 Years ★
    Participant

    Hai,
    Minitab uses in KW the z-score as follows:  “Z: A statistic used to determine how the mean for each group differs from the mean of all observations.” And then it calculates from these the H-value and the p-value. So the Z-scores are just help-calculations. I almost allways only use the P-value as outcome; the rest is needed to get to that value.
    General tip for Minitab if you do not understand a Minitab output (Analysis result or Graph): Use the StatGuide- Click the mousepointer in the output.- Click on the “Purple Sigma button with yellow background”; it is located directly to the right of the question mark in the Standard Toolbar of Minitab (the upper part of Minitab where you click on for Saving; Opening etc).
    You get a Help function (if properly installed by your IT) that explains clearly (not mathematically or IT-ly) what the output tries to tell you. With Example!
    Success

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