- Thread starter med1234
- Start date

So which test you use depends on what you planned. However, if the ANOVA itself is not significant then you really should not follow up with either type of test. You should only use these if the F tests is significant.

further information:

1) as data are not normal distributed, I have performed a 1-way ANOVA (Kruskal Wllis test with Dunn's multiple Comparison post-hoc testing)

2) On the other hand I have performed a Mann-Whitney test between each colomn

with ANOVA no significane... with Mann-Whitney some relevant significant differences... QUITE ASTONISHING: p>0.05 vs. highly signifant results with Mann-Whitney (p<0.001 and p<0.0001) !!!!!

For me it is absolutely not clear, when I am allowed to do a-priori-testing and when not... naturally, I intended to compare the according parameters before doing the experiments... (most people do?)

How to go on, now?

1) as data are not normal distributed, I have performed a 1-way ANOVA (Kruskal Wllis test with Dunn's multiple Comparison post-hoc testing)

2) On the other hand I have performed a Mann-Whitney test between each colomn

with ANOVA no significane... with Mann-Whitney some relevant significant differences... QUITE ASTONISHING: p>0.05 vs. highly signifant results with Mann-Whitney (p<0.001 and p<0.0001) !!!!!

For me it is absolutely not clear, when I am allowed to do a-priori-testing and when not... naturally, I intended to compare the according parameters before doing the experiments... (most people do?)

How to go on, now?

Last edited:

It's not that astonishing that you found significance when you did multiple a priori tests. As a metaphor it would be like having 3 green marbles and 10 red marbles in a bag. If you picked 10 marbles you're likely to pick a green marble (not to get too far off topic but the birthday paradox [google that too if you're unfamiliar with it] is a prime example of probability similar to family wise error).