(b) Let
Aand
Dbe nonsingular matrices of orders
kand
m, respectively,
Bbe
k\times m, and
Cbe
k\times m. Then, provided that the inverses exists
(A+BDC^('))^(-1)=A^(-1)-A^(-1)B(D^(-1)+C^(')A^(-1)B)^(-1)C^(')A^(-1). The inverses of the scatter matrices can be expressed as
(x^(')x)^(-1)=(x_((i))^(')x_((i))+x_(i)x_(i)^('))^(-1)and
(x_((i))^(')x_((i)))^(-1)=(x^(')x-x_(i)x_(i)^('))^(-1), where
x_((i))denotes the design matrix with the
ith observation deleted. Denote the predicted leverage as
h_(i(i))=x_(i)^(')(x_((i))^(')x_((i)))^(-1)x_(i)and deduce the relationship between the leverage values
h_(ii)=x_(i)^(')(x^(')x)^(-1)x_(i)and the predicted leverage
h_(i(i)), i.e., express
h_(i(i))as a function of
h_(ii). (c) Consider the studentized residuals (
t_(i)^(**)) and the deleted (externally) studentized residuals
t_(i)diagnostics. (i) Name the data aberration(s) diagnosed by
t_(i)^(**)and
t_(i), respectively. (ii) Give the respective expression (formula) for
t_(i)^(**)and
t_(i). (iii) Argue which one is a better measure between
t_(i)^(**)and
t_(i). (6)
