How to conduct Mann-Kendall test for trend analysis?

Answer 1

by using this formula

where y=data values at times i and j and n=length of the data set

and

Under the null hypothesis that yi are independent and randomly ordered, the statistic S is approximately normally distributed when n≥8, with zero mean and variance as follows:

The standardized test statistic ZS is computed by:

Decide on a probability level of significance (95% typically)

The trend is said to be decreasing if ZS is negative and the computed probability is greater than the level of significance. The trend is said to be increasing if the ZS is positive and the computed probability is greater than the level of significance. If the computed probability is less than the level of significance, there is no trend.

you can use Excel to compute the equations. Tq