I conducted a Friedman test to related-sample group in three conditions (pre-treatment, post-treatment and 6-month post treatment). Out of 216 participants that completed the first two stages, 50 of these completed the 6-month post stage. Am I right in thinking that the Friedman test is doing the calculation on the 50 participants that completed all stages?
My problem is that I then want to conduct a Wilcoxon signed ranks post hoc test to examine where the differences are. N = 216 participants as opposed to the 50 used in the Friedman test.
Could anyone tell me if it is ok to use this result? Or do I have to separate the data further so the Wilcoxon test uses the 50 participants? Does this impact its validity?
Any help would be greatly appreciated,