1,721,024 research outputs found
Application of Bayesian networks in Official Statistics
No full textIn this paper recent results about the application of Bayesian networks to official statistics are presented. Bayesian networks are multivariate statistical
models able to represent and manage complex dependence structures. Here they are
proposed as a useful and unique framework by which it is possible to deal with many
problems typical of survey data analysis. In particular here we focus on categorical variables and show how to derive classes of contingency table estimators in case of stratified sampling designs. Having this technology it becomes possible to perform
poststratification, integration and missing data imputation. Furthermore we briefly discuss how to use Bayesian networks for decision as a support system to monitor
and manage the data production process
BAYESIAN NETWORKS FOR FINITE POPULATIONS
No full textIn questo lavoro si propone uno stimatore della distribuzione di frequenze congiunta quando il campione è estratto con disegni campionari complessi tramite le reti Bayesiane. Questa formalizzazione può essere utile ai fini della valutazione delle politiche da parte di un decision maker. Un esempio nel settore dell'agricoltura viene discusso.In this work an estimator of the joint frequency distribution is defined when the sample is drawn according to complex survey designs by means of the Bayesian networks. This formalization can be useful for the evaluation of policies by a decion maker. An example in the agricultural sector is discussed
Uncertainty Analysis for statistical matching of ordered categorical variables
No full textThe aim is to analyze the uncertainty in statistical matching for ordered categorical variables. Uncertainty in statistical matching consists in estimating a joint distribution by observing only samples from its marginals. Unless very restrictive conditions are met, observeddatadonotidentifythejointdistributiontobeestimated,andthisisthereason of uncertainty. The notion of uncertainty is first formally introduced, and a measure of uncertainty is then proposed. Moreover, the reduction of uncertainty in the statistical model due to the introduction of logical constraints is investigated and evaluated via simulation
COHERENCE OF SAMPLE ESTIMATES FOR FINITE POPULATIONS: SOME RESULTS BASED ON BAYESIAN NETWORKS
No full textThe idea of coherence of estimates is crucial in the production process of the national
institutes of statistics. In this paper we consider the idea of internal and external coherence. The first
concept is related to results of a single survey while the second is related to results of different surveys.
It will be shown how Bayesian networks can be usefully exploited in order to define general estimators
in a finite population context
Uncertainty Analysis in Statistical Matching
No full textAmong the goals of statistical matching, a very important one is the estimation of the joint distribution of variables not jointly observed in a sample survey but separately available from independent sample surveys. The absence of joint information on the variables of interest leads to uncertainty about the data generating model. The present article reviews the concept of uncertainty in statistical matching and how to measure it by providing a unified framework for the parametric and nonparametric setting. Furthermore, the reduction of uncertainty due to the introduction of logical constraints is investigated and a simulation experiment is performed
On the Matching Noise of some Nonparametric Imputation Procedures
No full textThe aim of the paper is to evaluate the matching noise produced by nonparametric imputation techniques referring to the kNN
method, both with fixed and variable number of donors k. The matching noise is evaluated formally and via a simulation
Carta delle rocce ornamentali della Sardegna
No full textThe poster shows a collection of decorative stones extracted over the last fifty years in Sardinia.
The term decorative stone is used generically to refer to all natural stones that can be used as decorative material, mainly for cladding and covering and secondarily in a structural role. The term ornamental stone is also used. The international industry term is dimension stones.
Reflecting multiple geological events, the lithological Sardinian landscape has offered and still offers a remarkably wide range of possibilities for researching and gathering decorative stones, according to varying requirements, the main being chromaticism and workability, not forgetting other important characteristics such as hardness and durability.
The survey in the Regional Plan of Mining Activities (Piano Regionale delle Attività Estrattive - P.R.A.E.) for the Autonomous Region of Sardinia (Regional Law 30/89) identified eight “Dimension stone producing areas”, each of which features quarries for petrographically homogeneous rock types: granite (4), limestone (1), volcanic rocks (2, basalt and ignimbrites), metamorphic rocks (1
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