নিচের কোন সূত্রটি শুদ্ধ (প্রচলিত চিহ্নে)?

$r=\frac{{\displaystyle \sum _{i=1}^n}(x_i-\overline{x})(y_i-\overline{y})}{\sqrt{{\displaystyle \sum _{i=1}^n}(x_i-\overline{x}){\displaystyle \sum _{i=1}^n}(y_i-\overline{y}{)}^2}}$

$r=\frac{{\displaystyle \sum _{i=1}^n(x_i-\overline{x})\sum _{i=1}^n(y_i-\overline{y})}}{\sqrt{{\displaystyle \sum _{i=1}^n(x_i-\overline{x})\sum _{i=1}^n(y_i-\overline{y}{)}^2}}}$

$r=\frac{{\displaystyle \sum _{i=1}^n(x_i+)(y_i-\overline{y})}}{\sqrt{{\displaystyle \sum _{i=1}^n(x_i-\overline{x})\sum _{i=1}^n(y_i-\overline{y}{)}^2}}}$

$r=\frac{{\displaystyle \sum _{i=1}^n(x_i-\overline{x})(y_i-\overline{y})}}{\sqrt{{\displaystyle \sum _{i=1}^n\left[\right(x_i-\overline{x}\left)\sum _{i=1}^n\right(y_i-\overline{y}){]}^2}}}$

কোনোটিই নয়