Discrete Mathematics
# Variance

If the joint probability distribution function of $X$ and $Y$ is given as follows, what is $20 \text{Cov}(X,Y) ?$

$\begin{matrix} p(X,Y) & X=0 & X=1 & X=2 \\ Y=0 & 0.1 & 0.1 & 0.2 \\ Y=1 & 0.2 & 0.2 & 0 \\ Y=2 & 0 & 0.1 & 0.1 \end{matrix}$

For random variables $X$ and $Y,$ which of the following is the same as $\text{Cov}(X,Y)?$

If $X$ and $Y$ are independent random variables where $E[X]=10$ and $E[Y]=8,$ what is $E[XY]?$