Karl Pearson's correlation coefficient is calculated by which of the following formula?

A. $$\frac{{{\text{Covariance of X and Y}}}}{{{\text{Var}}{\text{.}}\left( {\text{X}} \right)\,{\text{Var}}{\text{.}}\left( {\text{Y}} \right)}}$$

B. $$\frac{{{\text{Covariance of X and Y}}}}{{\sqrt {{\text{Var}}{\text{.}}\left( {\text{X}} \right)\,{\text{Var}}{\text{.}}\left( {\text{Y}} \right)} }}$$

C. $$\frac{{{\text{Var}}{\text{.}}\left( {\text{X}} \right)\,{\text{Var}}{\text{.}}\left( {\text{Y}} \right)}}{{\sqrt {{\text{Covariance of X and Y}}} }}$$

D. $$\frac{{{\text{Var}}{\text{.}}\left( {\text{X}} \right)\,{\text{Var}}{\text{.}}\left( {\text{Y}} \right)}}{{{\text{Covariance of X and Y}}}}$$

Answer: Option B