[R] Repeated measures Tukey

Bert Gunter bgunter.4567 at gmail.com
Tue Nov 28 17:57:16 CET 2017

This list is about R programming help, not statistics, although they do
sometimes overlap. However, as this appears to be entirely a statistics
issue, it really belongs on a statistics list like stats.stackexchange.com
, not here.


Bert Gunter

"The trouble with having an open mind is that people keep coming along and
sticking things into it."
-- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )

On Tue, Nov 28, 2017 at 6:00 AM, Francesc Pla Juncà <cesc.pla at gmail.com>

> Thanks in advance for your help.
> I am running a repeated measures ANOVA in r. The same group undergoes to
> four different treatment conditions. So, all individuals are treated with
> treatments A, B, C and D in four different occasions.
> Once I get a significant ANOVA, I first run a paired samples t-test using
> the code:
> t.test(X1,X2,paired=TRUE) #being x1 the punctuation after treatment 1 and
> x2 the punctuation after
> treatment 2.
> After this, I run a Tukey posthoc test for repeated measures as stated in
> gribblelab:
> require(nlme)
> a1<-lme(x~factortmnt,random=~1|factorid/factortmnt,data=mydata)
> print(anova(a1))
> require(multcomp)
> summary(glht(a1,linfct=mcp(factortmnt="Tukey")))
> The fact is that once I get both results, there are some occasions in which
> I get lower p values with Tukeys correction than in paired t-tests.
> How is it possible? Isn't Tukey more restrictive than paired t-tests?
> Cesc
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