\(r_{\text{XY}}=\frac{\sum_{i=1}^{n}{(X_{i}-\overset{\overline{}}{X})(Y_{i}-\overset{\overline{}}{Y})}}{\sqrt{\sum_{i=1}^{n}{(X_{i}-\overset{\overline{}}{X})}^{2}\times\sum_{i=1}^{n}{(Y_{i}-\overset{\overline{}}{Y})}^{2}}}\) (9)