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Thread: Three way anova for repeated measure

  1. #1
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    Three way anova for repeated measure




    Hi all, I am struggling with how to properly fit a three way anova using STATA. It keeps giving me this error message "could not determine between-subject basic unit; use bseunit() option" and the solutions online do not seem to work for me.

    Summarizing my data:

    id = person identification
    bloodpressure = outcome measure, it is continuous and normally distributed
    gender = binary
    arm = binary (right or left arm)
    time = categorical (T1 T2 T3 T4)

    basically after a stimulation only on the right arm (the left arm is a control) I am measuring the variation of perioheral blood pressure over time and assessing possible gender differences.
    I have a total of 24 persons and for each person 4 measures for each arm ( 8 measures in total per person) for a total of 192 measures.

    My problem is that the sample size is relatively low, I fitted a linear mixed model without many problems (but afraid of possible bias due to sample size) and therefore wanted to compare it with a three way anova with an interaction between time and arm

    the code I used with STATA for the linear mixed model is the follow:

    xtmixed bloodpressure i.arm i.time i.gender i.arm##i.time || id: , covariance(unstructured) mle var

    followed by contrast time@arm, effect to study the effect size

    The results seem quite clear to me but still afraid that the approach is not completely right that is why I would like to compare it with a three way anova for repeated measures

    What would be the code in stata to do a three way anova with interaction between time and arm without having the error message? I have tried so many variations of the code but I keep having the error displayed above!

    Many thanks in advance for the help!

  2. #2
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    Re: Three way anova for repeated measure

    Maybe you'd better ask this in the STATA subforum?

    With kind regards

    K.

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    Re: Three way anova for repeated measure

    Yes, you are probably right but I don't know how to move the topic (probably only the admins can)

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    Re: Three way anova for repeated measure

    Simply post this again in the STATA forum and mention there
    that you had initially posted here.

    With kind regards

    K.

  5. The Following User Says Thank You to Karabiner For This Useful Post:

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    Re: Three way anova for repeated measure

    Why do you think a RM ANOVA will deal better with small samples than a multi-level model will?

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    Re: Three way anova for repeated measure


    Poster reposted thread here: http://www.talkstats.com/showthread....eated-measure?

    Post any comments in that thread.
    I don't have emotions and sometimes that makes me very sad.

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