Regional Kendall Test for Trend US Geological Survey, 2005 Data set: Example RK3b - Regional Kendal test, input type 3 The record is 12 years at 25 locations beginning in year 1993. The tau correlation coefficient is 0.281 S = 460. z = 6.345 p = 0.0000 The estimated median trend throughout the region during years 1993 through 2004 is: Change in Y = 0.1600 per year.