function [se,t,s2] = ols3b(y,X,bols);

n=length(y);% an alternative to size(y,1) for vectors
k=size(X,2);

e=y-X*bols;
s2=e'*e/(n-k); 
Vb=s2*inv(X'*X); 
se=sqrt(diag(Vb));
t=bols./se;