# What are the mean and standard deviation of a binomial probability distribution with n=13 and p=0.1?

Mean is $1.3$ and standard deviation is $1.08$.
As mean is given by $n \cdot p$, it is $13 \cdot 0.1 = 1.3$.
Standard Deviation is given by$\sqrt{n p q}$, where $q = 1 - p$. Hence $q = 0.9$ and
Standard Deviation is $\sqrt{13 \cdot 0.1 \cdot 0.9} = \sqrt{1.17} = 1.08$