The variance of 20 observations is 5. If each observation is...

Variance $\left(\sigma^2\right)=\sum_{i=1}^n f\left(x_i-\overline{\mathrm{X}}\right)^2$ when each observation is multiplied by $m$, then, Variance \left(\sigma^2\right)$=\sum_{i=1}^n m^2 f\left(x_i-\overline{\mathrm{X}}\right)^2$ Here, $m=2$, so, new variance \left(\sigma^2\right)=2^2 \times 5=20