Correlation

Summary statistics and the PMCC

The summary statistics $S_{xx}$, $S_{yy}$ and $S_{xy}$ measure spread and how $x$ and $y$ vary together. The product moment correlation coefficient $r=\dfrac{S_{xy}}{\sqrt{S_{xx}S_{yy}}}$ lies between $-1$ and $1$ and measures how close the points are to a straight line.