Hello folks, I am sure this is an easy question answered many times, but I need some refresh: When it comes down to compare fits using different models, which is the relevant parameter? Chi square (and reduced) or R-factor? I have fits with smaller chi square and larger Rfactor and viceversa... Is it possible that a rationale would be that when the models to compare have the same number of atoms these parameters go in parallel? And that when the number of atoms is different one must rely more on chi square rather than R-factor (or viceversa)? Oh well. Stefano -- ____________________________________________ Stefano Ciurli Professor of Chemistry Department of Agro-Environmental Science and Technology University of Bologna Viale Giuseppe Fanin, 40 I-40127 Bologna Italy Phone: +39-051-209-6204 Fax: +39-051-209-6203 "Fatti non foste a viver come bruti, ma per seguir virtute e canoscenza" Dante Alighieri - Inferno - Canto XXVI "Ihr seid bestimmt, nicht Tieren gleich zu leben, Nein, Tugend zu erringen und Erkenntnis" "Ye were not form'd to live the life of brutes, But virtue to pursue and knowledge high"