[R] Repeated measures Tukey

[Francesc Pla Juncà]

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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