title: Co-variance: Normalize by N or N-1?
body: <p>I'm working on calculating covariance by hand in matlab (without using the cov function). Anyway, I'm confused on why and when to normalize by N or N-1. I've been given sample data that is 2x400. Thus, two variable and 400 samples. Can anyone explain when a certain normalization is appropriate or is it slightly subjective? Thanks</p>