The question is as followed: Suppose n cards - numbered 1,2,...,n are shuffled and kept faced down, and we suppose the cards are turned over 1-by-1. Define $X_i$ to be:
1 if the i-th card card is turned over at the i-th stage
0 otherwise
We're told N = $\sum_{i=1}^{n}{X_i}$. Find E(N) and Var(N).
Through conditional probabilities, I find the P($X_i$=1) is 1/n for all I, which leads us to an E(N) = $1/n*n$ = 1
I'm not sure how to approach the covariance part of the variance? Any hints?