This applet was shared by tlindy and was slightly modified by JimD.[br]Move the scatter slider back and forth between "Strong Negative" and "Strong Positive" correlations.

Note that with a perfect negative correlation (r= -1.00), all of the points fall on the best-fitting line (r^2= 1.00).[br]Note that with a perfect positive correlation (r= +1.00), all of the points fall on the best-fitting line (r^2= 1.00).[br]Note that the "MnXMnY" point (Mean of the Xs, Mean of the Ys) always falls on the best-fitting line. [br]When r= 0, the best-fitting line provides no useful prediction (r^2= 0). The best one can do is to always predict (Mean of the Xs, Mean of the Ys).