estimates

Hi all, When I change the initial values, NM will give different estimates, with large or small differences. My questions are: 1. Which set of estimates can be mostly trusted and taken as the final estimates? 2. If the estimates change a lot, does it mean that the model is not stable and need to be improved? 3. When I have poor data ( observations are too little, or BSV is too big), sometimes I am not sure if the data or the model causes the unstable of the estimates. How can I know that the best results are reached and no more work is needed? Any advice is much appreciated. Paul School of Pharmacy University of Pittsburgh 716 Salk Hall 3501 Terrace Street Pittsburgh, PA 15261 Phone: 412-648-8546 E-mail: [email protected]