1. Statistically testing for correlation between precipitation anomalies versus
ENSO index (Niño 3.4 index).
• Pearson Correlation coefficient, r
oNull Hypothesis, H0
is no correlation
• Kendall’s Correlation coefficient, τ
oSince Pearson Correlation measures linear association and it is difficult
to satisfy this condition of a hydrologic variable being independent ,
normal random variable, Kendall’s correlation was also used as a
measure of correlation.
o Distribution-free rank correlation