I get a little bit confused by the conclusions I can take or not with these small samples.
I have been measuring the degradation of a pollutant for 9 days. I measured the remaining concentration and only took triplicates each day, so that gives me a very small sample size. I want to check at which point there is no significant difference between 2 days anymore. I first thought of anova followed by Tukey.
But then when i checked for normality, I did the Shapiro test for normality and my data didn't pass the test. That doesn't allow me to say my samples don't come from a normal distributed population, does it? What does it tell me then? And would the qqplot and histogram tell me more or is that also not very relevant with small samples?
And does that exclude me using ANOVA? Would a permutation test make sense? but I read the equivalent of Anova requires a lot of calculation time and that it wasn't used a lot..
I would be grateful if someone could clarify the situation a little bit ...