I apply the "effective degree of freedom" to get a
significance level when I calculate correlation coefficient?
T-test can be used for figuring out the significance level.
however, it's known that the effective degree of freedom
(Davis 1976, "Predictability of Sea Surface Temperature and
Sea Level Pressure Anomalies over the North Pacific Ocean")
need to be consider instead of using "N-2" for comparing two
variables which are closely related, such as local sea surface
temperature and global sea surface temperature.