----------------- HES POSTING ----------------- Look in Maddala's 1992 Introduction to Econometrics, (p. 389-395) he gives a fairly good overview of problem of distinguishing between endogenity and exogeneity (words???), and he does point to some more literature on the subject. Also look at his section on the Hausman test. Robert P. Rogers ------------ FOOTER TO HES POSTING ------------ For information, send the message "info HES" to [log in to unmask]