Five balls numbered $0,2,4,6,8$ are placed in a bag. After the balls are mixed, one of them is selected, its number is noted, and then it is replaced. If this experiment is repeated many times, find the variance and standard deviation of the numbers on the balls.
I choose $X=0,2,4,6,8$, and hence $f(0)= f(2)=f(4)=f(6)=f(8)= \frac15$. So I think to use the formula $\sigma^2=\mu_2-\mu^2$ to find variance where $\mu=\sum{xf(x)}$ and $\mu_2=\sum{x^2f(x)}$. This is what i think for this question!