An extremely strange observation on the equations for calculation of correlation coefficient.
Various equations are used to calculate the correlation coefficient, these equations are presumed equally. However we find the extraordinary results when using r = square root of ((sigma(ŷi - y)2) / (sigma(yi - y)2)) and r2 = (sigma(yi - y)2 - sigma(yi - ŷi)2) / (sigma(yi - y)2) to calculate the correlation coefficient, for example, a line within 95% confidence band of a regressed line. The results are so extraordinary that we do not know whether or not we can still call the results as correlation coefficient, however we are sure that these results need to be presented.
Wu
Guang
G
Laboratoire de Toxicocinétique et Pharmacocinétique, Faculté de Pharmacie, Université de la Méditerraneé Aix-Marseille II, Marseilles, France.
D016014:Linear Models; D008432:Mathematical Computing