Q:

n people put their watch in the center of a room where the watches are mixed

together. Each person then randomly selects one. Let X represent the number that select their own watch. Find the expected value and variance of X.

I found the expedted value to be 1. ( sum to n 1/n*1). So variance i have

sum 1/n(x_i - 1)^2 = 0

is the variance correctly 0?