A die is thrown 100 times, then the standard deviation of getting an even number is
A die is thrown 100 times, then the standard deviation of getting an even number is
10
5
20
15
Solution
Let $x$ denote the number of succeses in 100 Then $x$ follows binomial distribution with $n=1008$ $p=y_{2}, q=\frac{1}{2}$
$\therefore$ variance of $x=n p q=100 \times \frac{1}{2} \times \frac{1}{2}=25$
$\begin{array}{l}\text { Standard } \\ \text { Deviation }\end{array}=\sqrt{\text { vatiance }}=\sqrt{25}$
$=5$