1,721,205 research outputs found
Possibility theory: conditional independence
No full textThe subtle notion of conditioning is controversial in several contexts, for example in possibility theory where, in fact, different definitions have been introduced. We refer to a general axiomatic definition of conditional possibility and then we deal with “partial assessments” on (not necessarily structured) domains containing only elements of interest. We study a notion of coherence, which assures the extendability of an assessment as a conditional possibility and we introduce a procedure for checking coherence. Moreover, we propose a definition of independence for conditional possibility, which avoids some counterintuitive situations, and we study its main properties in order to compare it with other definitions introduced in literature. Then, we check which properties among the graphoid ones are satisfied: this allows to compare our definition with other independence notions given in the context of other uncertainty formalisms. This analysis is relevant for graphical models in order to single out and visualize dependence relations among random variables
A Dutch book coherence condition for conditional completely alternating Choquet expectations
Full text linkStemming from de Finetti’s coherence for finitely additive (conditional) probabilities, the paradigm of coherence has been extended to other uncertainty calculi. We study the notion of coherence for conditional completely alternating Choquet expectations, providing an avoiding Dutch book like condition
Sedimentology and palaeoecology of barnacle-dominated, Amphistegina-bearing facies from the lower Pliocene of Liguria (northwestern Italy)
No full text
Bayesian inference under ambiguity: Conditional prior belief functions
No full textBayesian inference under imprecise prior information is studied: the starting point is a precise strategy σ and a full B-conditional prior belief function BelB, conveying ambiguity in probabilistic prior information. In finite spaces, we give a closed form expression for the lower envelope P of the class of full conditional probabilities dominating BelB, σ and, in particular, for the related “posterior probabilities”. The assessment BelB, σ is a coherent lower conditional probability in the sense of Williams and the characterized lower envelope P coincides with its natural extension
Lower pliocene barnacle facies of western liguria (NW Italy): A peek into a warm past and a glimpse of our incoming future
Full text linkThe lower Pliocene deposits of Pairola (Liguria, Italy) display the otherwise rare occurrence of rock-forming amounts of barnacles (mostly belonging to the extinct Euromediterranean species Concavus concavus). Three main facies are recognised in the investigated succession: a barnacle-dominated facies, which formed along a shallow (<15 m deep) nearshore environment, a foraminifera-dominated facies from relatively deeper waters (40-100 m), and an intermediate facies forming at the boundary of the other two. These facies and their relationships suggest deposition in a flooded valley – a kind of setting that was common in the Mediterranean after the Messinian Salinity Crisis. Differing from other rias, the Pairola basin was exposed to strong waves, resulting in conditions favourable to barnacles. Sedimentological and stratigraphic observations indicate that the Pairola succession formed within a timespan covering both cold and warm phases. This is relevant because the sub-tropical foraminifer Amphistegina is ubiquitous throughout the succession. Amphistegina occurs in the Pliocene and lower Pleistocene (Gelasian) of Northern Italy, but not in the remainder of the Pleistocene, not even its warm portions. This genus is currently recolonizing the Mediterranean and is projected to reach the northern coast of the basin soon, foretelling that Anthropocene temperatures are going to overcome those of the late Pleistocene warm periods and reach those of the Pliocene
Dutch book rationality conditions for conditional preferences under ambiguity
No full textWe study preference relations on conditional gambles of a decision maker acting under ambiguity. Dutch book rationality conditions are provided under a linear utility scale, encoding either an optimistic or a pessimistic attitude towards uncertainty. These conditions characterize possibly incomplete preferences representable by totally alternating or monotone conditional functionals. In general, the uniqueness of the representation is not guaranteed, but it can be obtained by adding the hypothesis of existence of a conditional fair price for every conditional gamble. The given rationality conditions have a betting scheme interpretation relying on “penalty fees” for betting on strict preference comparisons
Non Additive Ordinal Relations Representable by Lower and Upper Probabilities
No full textWe characterize (in terms of necessary and sufficient conditions) binary relations representable
by a lower probability. Such relations can be non-additive (as the relations
representable by a probability) and also not "partially monotone" (as the relations representable
by a belief function).
Moreover we characterize relations representable by upper probabilities and those representable
by plausibility. In fact the conditions characterizing these relations are not
immedi~tely deducible by means of "dual" conditions given on the contrary events, like in
the numerical case
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