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
- whether the test I used (Friedman) is the correct for my purpose?
- whether the sequence in which I gave the samples affects my result from Friedman test?
- if what I have done is incorrect, what to do instead?