Dear all,
I have a quite basic questions about anova analysis in R, sorry for
this, but I have no clue how to explain this result.
I have two datasets which are named: nmda123, nmda456. Each dataset has
three samples which were measured three times. And I would like to
compare means of them with Posthoc test using R, following please see
the output:
(CREB, mCREB and No virus are the name of samples)
> nmda123
Values ind
1 6.7171265 CREB
2 5.0343117 CREB
3 6.9000000 CREB
4 0.1195394 mCREB
5 0.1221876 mCREB
6 0.1900000 mCREB
7 1.0000000 No Virus
8 1.0000000 No Virus
9 1.0000000 No Virus
> nmda456
Values ind
1 6.4486940 CREB
2 6.2277490 CREB
3 6.5000000 CREB
4 0.2000000 mCREB
5 0.3766052 mCREB
6 0.4000000 mCREB
7 1.0000000 No Virus
8 1.0000000 No Virus
9 1.0000000 No Virus
> TukeyHSD(aov(Values ~ ind, data = nmda456))
Tukey multiple comparisons of means
95% family-wise confidence level
Fit: aov(formula = Values ~ ind, data = nmda456)
$ind
diff lwr upr p adj
mCREB-CREB -6.0666126 -6.3289033 -5.8043219 0.0000000
No Virus-CREB -5.3921477 -5.6544383 -5.1298570 0.0000000
No Virus-mCREB 0.6744649 0.4121743 0.9367556 0.0005382
> TukeyHSD(aov(Values ~ ind, data = nmda123))
Tukey multiple comparisons of means
95% family-wise confidence level
Fit: aov(formula = Values ~ ind, data = nmda123)
$ind
diff lwr upr p adj
mCREB-CREB -6.073237 -7.5618886 -4.584585 0.0000392
No Virus-CREB -5.217146 -6.7057976 -3.728495 0.0000943
No Virus-mCREB 0.856091 -0.6325606 2.344743 0.2588450
So my question is No virus-mCREB group. Even I looked at the data by
eyes, there is big difference between no virus and mCREB in data
nmda123, but why the pvalue is 0.2588450, but in nmda456 data, the
pvalue is 0.0005382. But I can see there is bigger difference in
nmda123 than nmda456, I do not know why. Sorry for my inexperiences in
statistics.
Thanks for your reply and time!
Cheers,
Wei
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