XB, your colleague regression is as simple as X2 = X0 X1 X3 X4 as long as no assumption is violated here, then you should be ok.

On 7/5/07, Xiaobing Fang <xfang@lsu.edu> wrote: > Hi, > > A colleague asked me if he can do this multiple regression. He first > calculated differences from X1 and X2 and used it as the dependent variable > (Y). Then he wanted to run regression Y = X0 X1 X3 X4 where Y is the > difference between X1 and X2, and he wanted to put X1 as one predictor. X0, > X3, X4 are independent from Y. > > Can this multiple regression be done? Which assumption is violated? > > Thanks, > > Xiaobing >

-- =============================== "I am dying with the help of too many physicians." - Alexander the Great, on his deathbed =============================== WenSui Liu (http://spaces.msn.com/statcompute/blog) ===============================