COEFFICIENT MATRIX IS ALGORITHMICALLY SINGULAR

From: "Bachman, William (MYD)" bachmanw@iconus.com Subject: [NMusers] COEFFICIENT MATRIX IS ALGORITHMICALLY SINGULAR Date: Wed, August 11, 2004 1:42 pm Depending on your data and model, it may not be possible to get a successful Covariance Step to run. Lack of ability to get a successful coavariance step MAY be an indication of poorly etermined parameter estimates or not having obtained a global minimum during parameter estimation. Some things to try: 1. try different initial estimate to assure yourself that you have obtained a global minimum (this is standard modeling procedure and should always be done regardless of whether you have a successful covariance step). 2. examine your variance estimates, if any are very poorly estimated (either approaching zero or greater than 100%), consider removing their respective etas from the model. Removing the zero ones in particular is often successful in getting a covariance step to run. 3. change your model, simpler is usually better if possible. nmconsult@globomaxnm.com GloboMax LLC 7250 Parkway Drive, Suite 430 Hanover, MD 21076 Voice: (410) 782-2205 FAX: (410) 712-0737