Quote from Bob111:
no need to pay..save some for trading..
http://67.220.225.70/~gumm5981/spearman-correlation.htm
http://67.220.225.70/~gumm5981/perfect-correlation.htm
http://67.220.225.70/~gumm5981/correlation2.htm
http://67.220.225.70/~gumm5981/correlation-stuff.htm
probably exactly what you are looking for(second page)-
http://67.220.225.70/~gumm5981/PairsTrading.htm
Some of these explanations are downright dangerous. The raw regression of prices of a non-stationary time-series? Unless the prices are damn close numerically, this is going to cause people to lose money.