Search results for "Bayes"

Identifying territories using presence-only citizen science data : An application to the Finnish wolf population

2022

Citizens, community groups and local institutions participate in voluntary biological monitoring of population status and trends by providing species data e.g. for regulations and conservation. Sophisticated statistical methods are required to unlock the potential of such data in the assessment of wildlife populations. We develop a statistical modelling framework for identifying territories based on presence-only citizen science data. The framework can be used to jointly estimate the number of active animal territories and their locations in time. Our approach is based on a data generating model which consists of a dynamic submodel for the appearance/removal of territories and an observatio…

Non-monophyly of the “cydnoid” complex within Pentatomoidea (Hemiptera: Heteroptera) revealed by Bayesian phylogenetic analysis of nuclear rDNA seque…

2017

The “cydnoid” complex of pentatomoid families, including Cydnidae, Parastrachiidae, Thaumastellidae, and Thyreocoridae, is morphologically defined by the presence of an array of more or less flattened stout setae (called coxal combs), situated on the distal margin of coxae. These structures, suggested to prevent the coxal-trochanteral articulation from injuries caused by particles of soil, sand or dust, by their nature and function are unknown elsewhere in the Heteroptera. As such, coxal combs were regarded as a synapomorphy of this group of families, and enabled the definition of it as a monophylum. In this study, the monophyly of the “cydnoid” complex of families is tested for the first t…

Elaborazione e validazione di modelli dell’impatto antropico e dei cambiamenti climatici sulle qualità dei suoli in Sicilia, con particolare attenzio…

Il declino della sostanza organica e l’erosione idrica sono due fattori di rischio di degrado del suolo fra i più diffusi in Sicilia. In che misura è possibile contrastarli modificando le attività antropiche ed in particolare quelle in ambito agricolo? Lo scopo della presente ricerca di dottorato è stato quello di mettere a punto dei modelli che permettessero di spiegare le relazioni esistenti fra le azioni dell’uomo in ambito agricolo con la sostanza organica e con l’erosione idrica nei suoli siciliani, tenendo conto anche del clima. Le due indagini sono state svolte separatamente, in parallelo, in aree agricole della Sicilia occidentale per la sostanza organica, sull’intero territorio sic…

Bayesian temporal and spatio-temporal Markov switching models for the detection of influenza outbreaks

2017

Influenza is a disease which affects millions of people every year and causes hundreds of thousends of deads every year. This disease causes substantial direct and indirect costs every year. The influenza epidemic have a particular behavior which shapes the statistical methods for their detection. Seasonal epidemics happen virtually every year in the temperate parts of the globe during the cold months and extend throughout whole regions, countries and even continents. Besides the seasonal epidemics, some nonseasonal epidemics can be observed at unexpected times, usually caused by strains which jump the barrier between animals and humans, as happened with the well known Swine Flu epidemic, w…

Production and Efficiency in 21 Industrialized Countries from 1966 to 2007 to Analyse the Italy’s Decline: Application of a Stochastic Frontier Model…

2008

This paper uses a stochastic frontier production model to estimate the technical efficiency of 21 nations among the more industrialized countries in the world for the wide period from 1966 to 2007. A Cobb-Douglas with labour and capital as inputs, GDP as output and efficiency with exponential distribution appears to work good from a statistical point of view. This model is used to estimate in a bayesian approach the efficiency score of these 21 countries. The bayesian way, applied via Gibbs sampling, is here useful to avoid problems about the small number of observations. So, each efficiency score is obtained as mean of 10,000 draws. The results underline a general and progressive efficienc…

The Spatial Overlap of Police Calls Reporting Street-Level and Behind-Closed-Doors Crime: A Bayesian Modeling Approach

2021

Traditionally, intimate-partner violence has been considered a special type of crime that occurs behind closed doors, with different characteristics from street-level crime. The aim of this study is to analyze the spatial overlap of police calls reporting street-level and behind-closed-doors crime. We analyzed geocoded police calls in the 552 census-block groups of the city of Valencia, Spain, related to street-level crime (N = 26,624) and to intimate-partner violence against women (N = 11,673). A Bayesian joint model was run to analyze the spatial overlap. In addition, two Bayesian hierarchical models controlled for different neighborhood characteristics to analyze the relative risks. Resu…

Generalizability and Simplicity as Criteria in Feature Selection: Application to Mood Classification in Music

2011

Classification of musical audio signals according to expressed mood or emotion has evident applications to content-based music retrieval in large databases. Wrapper selection is a dimension reduction method that has been proposed for improving classification performance. However, the technique is prone to lead to overfitting of the training data, which decreases the generalizability of the obtained results. We claim that previous attempts to apply wrapper selection in the field of music information retrieval (MIR) have led to disputable conclusions about the used methods due to inadequate analysis frameworks, indicative of overfitting, and biased results. This paper presents a framework bas…

La falta de reproducibilitat de la investigació: L'estadística com a legitimació del resultat

2014

La investigació científica es legitima mitjançant la replicació dels seus resultats, però els esforços per replicar afirmacions enganyoses exhaureixen el finançament. Ens centrarem en una d’aquestes errades: els resultats de proves estadístiques que ofereixen falsos positius a causa de l’atzar. Els mètodes estadístics clàssics confien en un p-valor per a ponderar les proves enfront d’una hipòtesi nul·la, però les proves d’hipòtesis bayesianes ofereixen resultats més fàcils de comprendre, sempre que hom puga especificar distribucions a priori per a la hipòtesi alternativa. Descriurem noves proves, les UMPBT, tests bayesians que ofereixen una especificació per defecte de les alternatives a pr…

Improving statistical classification methods and ecological status assessment for river macroinvertebrates

2016

Aquatic ecosystems are facing a growing number of human-induced stressors and the need to implement more biomonitoring to assess the ecological status of water bodies is eminent. This dissertation aims at providing tools to reduce the costs and improve the accuracy of freshwater benthic macroinvertebrate biomonitoring. To improve the cost-e ciency, we consider automated classi cation and develop a novel classi er suitable for complex macroinvertebrate image data. To enhance the accuracy of macroinvertebrate biomonitoring, we study the statistical properties of the Percent Model A nity index crucial to current Finnish biomonitoring and the factors a ecting these statistics. Finally, we perfo…

Single-cell analysis of population context advances RNAi screening at multiple levels

2012

Isogenic cells in culture show strong variability, which arises from dynamic adaptations to the microenvironment of individual cells. Here we study the influence of the cell population context, which determines a single cell's microenvironment, in image‐based RNAi screens. We developed a comprehensive computational approach that employs Bayesian and multivariate methods at the single‐cell level. We applied these methods to 45 RNA interference screens of various sizes, including 7 druggable genome and 2 genome‐wide screens, analysing 17 different mammalian virus infections and four related cell physiological processes. Analysing cell‐based screens at this depth reveals widespread RNAi‐induce…