Question

In a $B.D.$ $n=400,P=\frac{1}{5}$. Its standard deviation is

• A. $10\times \sqrt{2}$
• B. $\frac{1}{800}$
• C. $4$
• D. $8$

Answer 1

Answer: (D)

$8$

In $B.D$, Standard deviation $=$ $\sigma =\sqrt{np(1-p)}$
$n=400$ and $p=$ $\frac{1}{5}$

$\sigma =\sqrt{400\times \frac{1}{5}\times \frac{4}{5}}$
$\sigma =8$