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Re: One-Way Anova Repeated Measures: Main effect is significant, but post-hoc tests are not significant

Posted by Bruce Weaver on Jan 03, 2014; 2:07pm
URL: http://spssx-discussion.165.s1.nabble.com/One-Way-Anova-Repeated-Measures-Main-effect-is-significant-but-post-hoc-tests-are-not-significant-tp5723746p5723761.html

Ryan Black wrote
Sorry, but I can't resist plugging the MIXED procedure. :-)
I'm shocked!  What next?  Jon promoting the use of Python, perhaps?  :-O


Ryan Black wrote
JohnDoe,

Under certain conditions, it's perfectly acceptable to employ the Tukey HSD
procedure as a follow-up procedure in testing all-possible pairwise
comparisons in a repeated measures ANOVA. While it might take a little bit
of effort, this procedure can be employed in SPSS for your design.

But let's step back for a moment. What is your understanding of the
assumption of sphericity? How could a departure in sphericity affect the
the sampling distribution of the ratio of mean squares? Are you familiar
with the index, espilon? What is your estimate of epsilon?  What is your
understanding of the rule(s) of thumb regarding epsilon? What are the
corrections offered by SPSS?

I really appreciated Bruce's question/comment about the "...nature of the
repeated measures factor." It could have an impact not only on the post-hoc
tests performed but the model as well (e.g., general linear model versus
linear mixed model). For example, if your repeated measures variable is a
measure of time, it's possible to observe a decay in correlations between
residuals from observations more distant in time. This type of residual
correlation structure could be modeled in the MIXED procedure. Sorry, but I
can't resist plugging the MIXED procedure. :-)

Ryan


On Thu, Jan 2, 2014 at 12:13 PM, JohnDoe <[hidden email]> wrote:

> Thanks,
>
> As it was a repeated measures test, I was unable to select any post hocs
> except for LSD, Bonferroni, and Sidak. I have four levels in my design
>
>
>
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--
Bruce Weaver
bweaver@lakeheadu.ca
http://sites.google.com/a/lakeheadu.ca/bweaver/

"When all else fails, RTFM."

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