Do the fixed effects regression assumptions in Key Concept 10.3 imply that (operatorname{cov}left(widetilde{v}_{i t}, widetilde{v}_{i s} ight)=0) for (t eq s) in Equation (10.28)? Explain.

Do the fixed effects regression assumptions in Key Concept 10.3 imply that \(\operatorname{cov}\left(\widetilde{v}_{i t}, \widetilde{v}_{i s}\right)=0\) for \(t eq s\) in Equation (10.28)? Explain.

Equation (10.28)

var (ni) = V2 var()-(+ Vit = var (V + 2 + + VIT) = -var (PA) +var (2) ++ var (vir) ... +2cov(2) + + 2cov(ViT-1, ViT)].