Search results for " statistica"

Separate regression modelling of the Gaussian and Exponential components of an EMG response from respiratory physiology.

2014

If Y1 \sim N(\mu ;\sigma^2) and Y2 \sim Exp(\nu), with Y1 independent of Y2, then their sum Y = Y1 +Y2 follows an Exponentially Modified Gaussian (EMG) distribution. In many applications it is of interest to model the two components separately, in order to investigate their (possibly) different important predictors. We show how this can be done through a GAMLSS with EMG response, and apply this separate regression modelling strategy to a dataset on lung function variables from the SAPALDIA cohort study.

A flexible approach for modelling a proportion response variable: Loss given default

2016

Loss given default (LGD) is a proportion of a credit exposure that is lost if the obligor defaults on a loan. Response variable LGD contains values between 0 and 1 including both 0 and 1, where 0 means that the balance is fully recovered while 1 means total loss of exposure at default. This article addresses two alternative semi parametric approaches for modelling loss given default, which is measured on the interval [0,1]. The class of models are very flexible and can accommodate skewness and bimodal characteristics of LGD data. The dependence of the predictors of each of the parameters (of the proposed model distribution for LGD) on explanatory variables can be additive P-splines, regress…

Modelling Spatio-Temporal Elephant Movement Data: a Generalized Additive Mixed Models Framework

2014

This thesis focuses on understanding how environmental factors influence elephant movement and in investigating the spatio-temporal patterns. The thesis analyses movement data of some African elephants (Loxodonta Africana) living in the Kruger National Park and its associated private reserves of South Africa. Due to heterogeneity among elephants, and nonlinear relationships between elephant movement and environmental variables, Generalized Additive Mixed Models (GAMMs) were employed. Results showed delayed effects of rainfall and temperature and particular trends in time and space.

Tuning parameter selection in LASSO regression

2016

We propose a new method to select the tuning parameter in lasso regression. Unlike the previous proposals, the method is iterative and thus it is particularly efficient when multiple tuning parameters have to be selected. The method also applies to more general regression frameworks, such as generalized linear models with non-normal responses. Simulation studies show our proposal performs well, and most of times, better when compared with the traditional Bayesian Information Criterion and Cross validation.

Non-communicable diseases, socio-economic status, lifestyle and well-being in Italy: An additive Bayesian network model

2018

The aim of the paper is to investigate the statistical association, on a sample of Italian subjects, extracted by Survey of Health, Ageing and Retirement in Europe (SHARE) dataset, between chronic diseases (occurrence or number of chronic diseases) and socio-economic and behavioural determinants (lifestyle indicators, QoL indicators, cognitive functioning variables). To this aim, additive Bayesian network (ABN) analysis was used. The resulting ABN model shows that better educated individuals have better health outcomes, age is direct and gender is an indirect determinant of the number of chronic diseases. Furthermore, self-perceived health is associated with lower number of chronic diseases…

Influence diagnostics for generalized linear mixed models: a gradient-like statistic

2013

In the literature, many influence measures proposed for Generalized Linear Mixed Models (GLMMs) require the information matrix that can be difficult to calculate. In the present paper, a known influence measure is approximated to get a simpler form, for which the information matrix is no more necessary. The proposed measure is showed to have a form similar to the gradient statistic, recently introduced. Good performances have been obtained through simulation studies.

Further considerations on a new indicator for higher education student performance

2016

Il presente lavoro si inserisce nel dibattito internazionale sul sistema di voto universitario e sulla sua sintesi come misura della performance di uno studente. Partendo dalla nuova misura proposta in Adelfio et al. (2014), in questo breve articolo si pone l’enfasi sull’importanza della scelta della misura opportuna, soprattutto nella individuazione delle possibili determinanti della performance, utile nella scelte delle opportune politiche di intervento sulla performance della carriera dello studente. Per richiamare il nuovo indicatore proposto e per fare il confronto con quello esistente, si `e fatto riferimento ai Sistema Universitario italiano. This paper joins the international debate…

Identification and modeling of stop activities at the destination from GPS tracking data

2021

Il presente articolo ha lo scopo di analizzare il comportamento turistico a destinazione, con un focus specifico sulle soste effettuate dai turisti nella destinazione. Vengono analizzati dati desunti da dispositivi GPS raccolti su un campione di crocieristi, a partire dai quali e possibile individuare le soste a destinazione `attraverso l’impiego di un opportuno algoritmo. L’effetto delle caratteristiche sociodemografiche e legate all’itinerario intrapreso sul numero di soste effettuate viene studiato attraverso l’impiego di modelli di reggressione di Poisson. I risultati sono di interesse sia da un punto di vista metodologico, legato all’analisi e sintesi di dati GPS, che dal punto di vist…

Tourism expenditure and tourism intra-destination mobility

2022

Approccio differenziato per la validazione dei dati GPS provenienti dalla rete UNIPA

2011

In questo lavoro ci si è proposti la verifica di qualità iniziale e la successiva elaborazione delle osservazioni provenienti dalle stazioni permanenti appartenenti alla rete dell’Università di Palermo, creata nell’ambito del progetto PRIN2005 dal titolo: “Reti di stazioni permanenti GPS per il rilievo in tempo reale in impieghi di controllo e emergenza” e gestita dal Dipartimento di Ingegneria Civile, Ambientale e Aerospaziale. Tale rete attualmente è formata da nove stazioni permanenti localizzate presso la Facoltà di Ingegneria dell’Università di Palermo e altri istituti o enti pubblici presenti nelle località di Termini Imerese (PA), Trapani, Agrigento, Caltanissetta, Partinico (PA), Ca…