Hi all:

We have datasets of temp and precipitation over time that we are attempting to calculate the mean change over different time periods and whether that change is significant. I found the excel formula below on another forum to calculate the mean change but am unsure whether it's proper. It does work but the mean change results are extremely low. Any ideas?:

=(INDEX(DJ2:DJ126,COUNT(DJ2:DJ126))-DJ2)/(COUNT(DJ2:INDEX(DJ2:DJ126,COUNT(DJ2:DJ126)))-1)

Also how would we test the significance of this change?

Thank you!
Jay