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Thread: Unbalanced ANCOVA

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    Unbalanced ANCOVA




    Hi all,

    I have data in this format:
    2 independent variables: 1 factor with 3 levels (3 different locations)
    1 continuous IV (depths)
    Dependent variable: Area of coral

    1) I want to test for the effect of both depth and site and look for an interaction between the two, so I am thinking I should use ANCOVA, or should I group the depths into 15,30,60 and 90 (as they are clumped like that-see attachment) and do factorial ANOVA?
    2) However, my data is unbalanced. I have 9 repeats for site a, 11 for b and 12 for c. I could make it balanced by using 9 repeats for all sites, but I would lose data. Can I analyse the unbalanced data, and if so, how? I've heard you can maybe use something called type 3 SS but I don't really understand how that applies to ANCOVA.
    3) Finally, I have different numbers of repeats at each depth (see attachment), does this matter, or only if I'm doing factorial ANOVA?
    Sorry for all the questions, any help would be much appreciated!
    Attached Images  
    Last edited by smed; 06-12-2017 at 11:06 AM.

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