Paired, continuous observations were compared by using the Wilcoxon test, and independent groups were compared by using the Mann-Whitney U test.
Because we do not know that the values have normal distribution, the Wilcoxon test is preferred over the Student's t-test.
For the statistical analysis, we compared the number of worms eaten by minnows to an expected random distribution using a Wilcoxon test.
For the Wilcoxon test, the test statistics is the sum of the ranks in the first sample, and the distribution of this statistics under the null hypothesis does not depend on the distribution of the two populations.
To estimate the health of trees in each year at the individual level, the AGR of a tree in a given year was compared with the AGR in the previous year using a Wilcoxon test.
Origin
1960s: named after Frank Wilcoxon (1892–1965), Irish statistician.