Usage of the Friedman test

I have done an experiment in which I have measured the energy required to chew three different food samples on 10 subjects with 3 repetitions per sample. I am interested therefore in finding out whether there is a difference between samples according to the energy consumed.

I have performed a Friedman test by ranks followed by multiple comparison procedure (Tukey's honestly significat difference for ranks) as Friedman test was significant.

However someone told me that for using that test I should make sure that the error for order effect was not significant, ans I don't fully understand this.

I provided my samples in the same order for all subjects. That is A,B,C -A1 B1 C1 and A3 B3 C3 for each subject.

I will be very grateful if you can tell me

1. whether the test I used (Friedman) is the correct for my purpose?
2. whether the sequence in which I gave the samples affects my result from Friedman test?
3. if what I have done is incorrect, what to do instead?
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Well, if the same individual tries to chew three different food samples then your groups are related/dependent. The Friedman test assumes the dependency and it is a distribution free test. You probably should do the Friedman test followed by post-hoc Nemenyi test (pp.11-12)"proposed" by Schaich and Hamerle. But it is likely your data are normal or try to normalize them to do 1-way RM ANOVA test, a parametric analogue of the Friedman test. IMHO – stan Oct 20 '11 at 10:35
– stan Oct 20 '11 at 10:40
Links2: R, R2, discussion. I'm newbie in statistics but I'm also trying to do Friedman+Nemenyi in R... Hopefully this information will help us :) – stan Oct 20 '11 at 10:41
Friedman's test is likely to assume a single observation, but you did in triplicates. Perhaps this is a vote for 1-way RM ANOVA... – stan Oct 21 '11 at 12:00