a statistical measure of the degree to which two sets of data are correlated according to the formula:
Rs = (1 - 6x ∑d2) / (n3-n)
where d - is the difference between the rank values of the data sets. While it can show how strongly data is correlated it is not a measure of cause and effect.
Geography Dictionary & Glossary for Students \\ ITS Tutorial School (ITS) - Hong Kong.