🚀 go-pugleaf

Hi,
I have a problem that I have not been able to sort out and would 
certainly appreciate some help.

In the regression model y = X*B + e
by writing y = x*B1 + Xs*Bs + e
where x is a T-vector, B1 a scalar, Xs a T*(K-1) matrix and Bs is 
a (K-1) vector.

The result var(B1) = sigma^2 / summation(x - xbar)^2(1-R^2)
can be derived (but how it is derived is the problem I cannot solve)
by applying partitioned inversion to X'X 
which comes from 
var-cov(b) = sigma^2(X'X)^-1

R^2 is the coefficient of determination obtained by regressing x on 
Xs.


This is a problem that has annoyed me for some days and if any one can 
shed some light on the matter I would certainly appreciate their help.
================================================================================
Alan Baker                             AARNET:  BAKER@COVAX.COMMERCE.UQ.OZ.AU
Department of Commerce                 TELEPHONE: Work  07 365 6686
University of  Queensland, QLD 4072    International  +617 365 6686
Australia	                                   Home 07 371 1386
================================================================================