[Forum SIS] Seminario POPPE

[Matteo Ruggiero]

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STATISTICS SEMINARS  -  COLLEGIO CARLO ALBERTO
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Venerdi' 24 Maggio 2013, alle ore 10:30, presso la sala rossa del 
Collegio Carlo Alberto, Moncalieri (TO), si terra' il seguente seminario:


STEPHAN POPPE (University of Leipzig, Germany)

	
SPECIES SAMPLING PROCESSES: PREDICTING THE 
UNPREDICTABLE AND ESTIMATING MEASURES OF DIVERSITY


Abstract:

The sampling of species problem relates to the issue of how to 
infer the relative species abundances from finite data, when 
many species occurring in the population are not present in the 
sample. Although these abundances can be seen to be the 
ultimate measure of the diversity in a population, there is also 
some interest in estimating particular summarizing diversity 
indexes such as  the Shannon index and the actual number of 
occurring species in the population.
The invocation of finite-dimensional symmetrical Dirichlet priors 
yields Bayesian statistical models which allow for a straight-forward 
inference of these abundances in case of a prefixed space of 
species, whereas their infinite-dimensional counterpart in form 
of the Pitman-Yor-process allows predictions for the case of 
previously unknown species.
The adoption of these models is usually mainly due to their 
analytical simplicity and the conjugacy of the underlying priors, 
but can also be justified from such predictive principles as 
exchangeability and Johnson’s sufficientness postulate. Hence, 
entertaining a dualistic point of view, i.e. looking at both the 
statistical model and the associated prediction rules, we 
potentially gain a better understanding of the inductive inference 
procedures set up. This becomes in particular important as the 
Dirichlet prior and the Pitman-Yor process do not lead to sensible 
estimates of neither the Shannon index nor the number of 
occurring species.
In my talk I will review several “classical” inductive characterizations 
of prediction rules of  authors such as Johnson, Carnap, Hintikka, 
Niiniluoto, Kuipers and Zabell. I will also show how the recently 
introduced species sampling model of Gnedin and Pitman fits in 
those inductive frameworks. If time permits, I will also shortly 
demonstrate their utility in improving the estimation of diversity 
indexes.



Tutti gli interessati sono invitati a partecipare.

Il seminario e' organizzato dalla "de Castro" Statistics Initiative
(http://www.carloalberto.org/stats) in collaborazione con il 
Collegio Carlo Alberto.
Il programma dei seminari puo' essere consultato alla pagina
http://www.carloalberto.org/events/seminars/statistics/


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Matteo Ruggiero
University of Torino & Collegio Carlo Alberto
http://web.econ.unito.it/ruggiero

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