Want to know how L.A.'s incoming supt. John Deasy (the man from Gates) is going to sort good teachers from bad? How he's going to decide who gets fired and who stays? Who has their careers destroyed? Who will get paid? How much?
It's all right here:
y = Xβ + Zv + ε where β is a p-by-1 vector of fixed effects; X is an n-by-p matrix; v is a q-by-1 vector of random effects; Z is an n-by-q matrix; E(v) = 0, Var(v) = G; E(ε) = 0, Var(ε) = R; Cov(v,ε) = 0. V = Var(y) = Var(y - Xβ) = Var(Zv + ε) = ZGZT + R.