On Apr 10, 12:49 am, davidlcass...@MSN.COM (David L Cassell) wrote: > shawn.hask...@TTU.EDU wrote: > > >On Apr 9, 12:53 am, davidlcass...@MSN.COM (David L Cassell) wrote: > > > o...@yahoo.com wrote: > > > > >Does any one konow any referance on bayesian multilevel zero-inflated > > > >negative binom? > > > > >all the best, > > > > >Oslo > > > > Are your data really suited to such an analysis? > > > > Please write back to SAS-L first and explain what your data are, and > > > where they come from, and how they were collected, and what you > > > want to do with them, and what the project goals are. Then people > > > here can give more helpful suggestions. > > > > HTH, > > > David > > > -- > > > David L. Cassell > > > mathematical statistician > > > Design Pathways > > > 3115 NW Norwood Pl. > > > Corvallis OR 97330 > > > > _________________________________________________________________ > > > Download Messenger. Join the i'm Initiative. Help make a difference > >today.http://im.live.com/messenger/im/home/?source=TAGHM_APR07 > > >Don't mean to hijack your thread, but I was actually wondering about > >this myself the other day. Zero-inflated Poisson exists, does zero- > >inflated NegBin? If so, how so in SAS? i have used PROC GENMOD for > >negbin GLM with offset before. > > >In wildlife studies we often examine habitat selection - i.e., > >resource selection functions that are often modeled with logistic > >regression as 'used' vs either 'unused' or 'available'. Those last 2 > >words carry a lot of baggage that we need not get into. Anyhow, > >sometimes the study area is broken into small plots using GIS or some > >other means. With new satellite and GPS technologies for tracking > >animals - you could end up with some used plots having 10, 20, 50, etc > >animal locations. A situation where the variance becomes much larger > >than the mean b/c you typically have many many more plots with zero > >uses - hence, a zero-inflated negative binomial? Also, you can use > >mixed models to deal with dependency of observations in order to > >separate individualistic effects vs population level effects. thanks. > > >Shawn H > > You know, it's so rare that someone starts out with a scientific model > that leads to a logical investigation of a ZINB model. Thanks. I needed > that. :-) > > The place to look is in the SAS-L archives. Look up Dale McLerran's > tomes on PROC NLMIXED for ZIP and ZINB models. Oh, and when > you do, don't look for his name in the 'author' box, because he uses > the 'from' name stringplayer2 . > > HTH, > David > -- > David L. Cassell > mathematical statistician > Design Pathways > 3115 NW Norwood Pl. > Corvallis OR 97330 > > _________________________________________________________________ > Exercise your brain! Try Flexicon.http://games.msn.com/en/flexicon/default.htm?icid=flexicon_hmemailtag...- Hide quoted text - > > - Show quoted text -

David, thanks for the tip, I'll check it out. The situation I gave was pretty particular b/c it was on my mind at the time. However, a ZINB model may actually be fairly common for a lot of wildife surveys. The reason is that many wildlife species are gregarious but not terribly common. Say you want to model factors affecting duck use of ponds. You visit 30 ponds and find no ducks, but when you do find a pond with ducks there might be 50, 500, or 1000. You might standardize the model by using pond area as an offset to get density but that is another matter. Anyhow, thanks for the help.

Shawn Haskell Texas Tech Univ PhD candidate, Wildlife Science