function [ b, seb, ty, e1] = OLS( Z )
%OLS Estimation
[T,a]=size(Z);
dep=Z(:,1);
ind=Z(:,2:a);
b=inv(ind'*ind)*(ind'*dep);
c=a-1;
e1= dep-ind*b;
SSE=e1'*e1;
sig2=SSE/(T-c);
covb=sig2*inv(ind'*ind);
seb=sqrt(diag(covb));
ty=b./seb;
end