# Math Help - covariance matrix

1. ## covariance matrix

This is a stupid question, but is this the formula to calculate the covariance matrix?

X'X? or is it the inverse of that?

2. the inverse of X'X is the variance-covariance matrix of the parameter estimates

3. I'm guessing what is being asked here is...

$V(\hat\beta)=\sigma^2(X^tX)^{-1}$

for the classical linear model.

4. yeahh well actually the question in my homework was actually what is the use of X'X? so i was just confirming it that could become the variance covariance matrix so i have something to say.

but thanks guys