Year

Mean

Mann-Whitney U

Wilcoxon

Z-Statistics

Asymptotic

Significant (2 Tailed)

Sen’s Estimator

Number of Samples

1971-1980

1981-1990

8.7

12.3

32

87

−1.361

0.174

1.841

10

10

1991-2000

2001-2010

11.3

9.7

42

97

−0.605

0.545

−0.211

10

10