If I have two signals $x$ and $y$ and this expression $E\{x[n]y[n-k]\}$, what is the expected value of the product?
I have a basic understanding of EV based on probability, such as $$E[X]=\sum_{i=1}^{\inf}x_ip_i$$ and I understand that EV of flipping coin is 0.5 if $x_1=0$ and $x_2=1$ and both probabilities are 0.5 or for rolling a dice is 3.5 etc.
However, when I see the expression like this the one above, I find it confusing. I don't know for instance where the probability term is.