Which of these defines the standard deviation of a Binomial distribution X∼Binomial(n=20,p=0.2)X \sim Binomial(n=20, p=0.2)X∼Binomial(n=20,p=0.2)?
20×0.2×0.8\sqrt{20 \times 0.2 \times 0.8}20×0.2×0.8
20×0.220 \times 0.220×0.2
20×0.2×0.820 \times 0.2 \times 0.820×0.2×0.8
20×0.2\sqrt{20 \times 0.2}20×0.2