X transpose X inverse, X Transpose Y, it's the best linear unbiased estimator (B.L.U.E. eh hem), and let me tell you whyyy,<p>Because ...<p>ah crap it's been to long, did anybody else learn this song in grad school for econometrics (or similar) when studying Gauss Markov theory?<p>Here's to Professor Jackson at Auburn for this memory I can never quite remember the second line of, and yet I can never quite forget the whole thing...