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Thread: MANOVA versus t-tests : unconsistent results

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    MANOVA versus t-tests : unconsistent results




    Hi,

    here is my problem. I am trying to compare the change on a language measure from time 1 to time 2 between 2 groups.

    If i do a repeated measures t-test for each group (between t1 and t2), i get a significant improvement in 1 group, and no significant change in the other group. (A result that I am happy with since my hypothesis was that there would be differential outcome of an intervention for 2 groups).

    If i conduct a mixed between-within subjects ANOVA, there is no interaction effect, but there are main effects for time and for group.

    (Also, this happens for basically all my variables!!! Not only my language score).

    1) how is that possible
    2) what can i do?

    Thank you very much

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    Re: MANOVA versus t-tests : unconsistent results

    Hi there,

    I think you may be coming across the issue that The Difference Between “Significant” and “Not Significant” is not Itself Statistically Significant.

    I.e. the change in mean between t1 and t2 is significant in one group and not in the other. But the change in mean in group 1 is not significantly different to the change in mean in group 2. This may seem confusing, but isn't inconsistent as such: these tests are asking different questions.

    If your hypothesis is that one group should have a greater mean change than the other, then this hypothesis is not supported.

    By the way, a MANOVA is something different to a mixed ANOVA (MANOVA has multiple response variables).

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    maxmon89 (07-28-2014)

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    Re: MANOVA versus t-tests : unconsistent results

    Wow, thank you so much! Very helpful and clear

    However, i feel kind of stupid but i'm not sure i understood your comment about MANOVA and mixed ANOVA. Could you elaborate a bit more?
    Thank you very much

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    Re: MANOVA versus t-tests : unconsistent results


    Quote Originally Posted by maxmon89 View Post
    However, i feel kind of stupid but i'm not sure i understood your comment about MANOVA and mixed ANOVA. Could you elaborate a bit more?
    MANOVA = multivariate analysis of variance. More than one dependent variable/response variable.
    Mixed ANOVA has just one dependent variable, but both fixed and repeated independent variables.

    Hope that helps!

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