Suppose (Xi, i) are IID as pairs for i = 1,...,n, with E(i) = 0 and var(i) = σ2. Here Xi is a 1×p random vector and i is a random variable (unobservable). Suppose E(X

iXi

) is p×p positive definite.

Finally, Yi = Xiβ +i where β is a p×1 vector of unknown parameters.

Is OLS biased or unbiased? Explain.