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CATEGORIES:National Centre for Statistical Ecology (NCSE) Sem
inars
SUMMARY:Modelling Pollock egg counts from the western Gulf
of Alaska by a zero-inflated Bayesian hierarchica
l space-time model - Geir Storvik\, University of
Oslo\, Norway.
DTSTART;TZID=Europe/London:20071127T123000
DTEND;TZID=Europe/London:20071127T133000
UID:TALK9188AThttp://talks.cam.ac.uk
URL:http://talks.cam.ac.uk/talk/index/9188
DESCRIPTION:Data from egg sampling surveys often contain a mix
ture of zero observations and large count or densi
ty values\, often with a high proportion of zeros.
We will consider a particular dataset giving wall
eye Pollock egg counts from the western Gulf of Al
aska\, from Kodiak Island to Unimah Pass\, in the
years 1978-2000. The main interest will be to pred
ict the intensity of eggs as a process varying in
space and time (both within and between years). In
this talk I will discuss a Bayesian approach for
the analysis of such data. The excessive number of
zeros in the data is taken into account by the us
e of a two stage modelling approach\, resulting in
a zero-inflated hierarchical space-time model. An
underlying intensity process is assumed to both i
nfluence the probabilities of zeros and the amount
of eggs in non-zero observations. Dependence of c
ovariates and spatio-temporal correlations are tak
en into account through the modelling of the under
lying intensity process. Fitting is performed thro
ugh Markov Chain Monte Carlo simulations. Results
for the walley Pollock egg counts will be presente
d.\n\nThis talk will be based on joint work with I
ngunn Tvete and Bent Natvig at the University of O
slo and Lorenzo Ciannelli at Oregon State Universi
ty.
LOCATION:Center for Mathematical Sciences\, room EL.09
CONTACT:Dr. Leah R Johnson
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