RE: Model building algorithm

From: "Bachman, William" <bachmanw@globomax.com> Subject: RE: Model building algorithm Date: Fri, 21 Apr 2000 15:29:21 -0400 I'd like to add a few comments to my previous statement regarding the addition of etas in a model. (Give me enough rope, so to speak ...) The objective function should not be the only criteria for model acceptability. In fact, in some cases the magnitude of the drop in objective function can be deceptive. One also needs to be concerned with the size of the variances estimated (as well as the array of diagnostic plots, etc.) In the extremes, if the variances go to zero, the data does not support those etas. If the variances are huge, they are driving the model and the parameter they are associated may not be supported by the data. On the other, I have seen instances where the variances appeared huge using the FO method, but, were more modest when the FOCE method was applied, so it appears that those etas should be part of the model. William J. Bachman, Ph.D. GloboMax LLC Senior Scientist 7250 Parkway Drive, Suite 430 Hanover, MD 21076 Voice (410) 782-2212 FAX (410) 712-0737 bachmanw@globomax.com