Help on which test to choose for paired samples?

#1
Hi there -

I'm hoping to elicit help on which test to choose - Mann-Whitney vs Wilcoxin (signed rank or rank-sum)? I have paired water samples and am analyzing the number of plankton (ranges from 0-15). The samples are paired because they were taken at the same location on the reef, once during daylight and once during dusk. I want to compare the number of plankton during daylight and at dusk. Any help would be greatly appreciated!

Thanks!
Lindsey
 
#2
Wilcoxon signed-rank test would be used if you have pairs, which it sounds like you have.

Mann-Whitney/rank-sum test whether two INDEPENDENT samples are statistically from the same population. I don't think you can treat your samples as independent.
 
#3
Great, thank you very much! I believe they are paired since they were taken from the same location (just at different times). I appreciate your help!

Wilcoxon signed-rank test would be used if you have pairs, which it sounds like you have.

Mann-Whitney/rank-sum test whether two INDEPENDENT samples are statistically from the same population. I don't think you can treat your samples as independent.