Search results for "Bay"
showing 10 items of 1187 documents
Efficient Bayesian generalized linear models with time-varying coefficients : The walker package in R
2020
The R package walker extends standard Bayesian general linear models to the case where the effects of the explanatory variables can vary in time. This allows, for example, to model the effects of interventions such as changes in tax policy which gradually increases their effect over time. The Markov chain Monte Carlo algorithms powering the Bayesian inference are based on Hamiltonian Monte Carlo provided by Stan software, using a state space representation of the model to marginalise over the regression coefficients for efficient low-dimensional sampling.
Bayesian Analysis of Population Health Data
2021
The analysis of population-wide datasets can provide insight on the health status of large populations so that public health officials can make data-driven decisions. The analysis of such datasets often requires highly parameterized models with different types of fixed and random effects to account for risk factors, spatial and temporal variations, multilevel effects and other sources on uncertainty. To illustrate the potential of Bayesian hierarchical models, a dataset of about 500,000 inhabitants released by the Polish National Health Fund containing information about ischemic stroke incidence for a 2-year period is analyzed using different types of models. Spatial logistic regression and…
Can visualization alleviate dichotomous thinking? Effects of visual representations on the cliff effect
2021
Common reporting styles for statistical results in scientific articles, such as $p$ p -values and confidence intervals (CI), have been reported to be prone to dichotomous interpretations, especially with respect to the null hypothesis significance testing framework. For example when the $p$ p -value is small enough or the CIs of the mean effects of a studied drug and a placebo are not overlapping, scientists tend to claim significant differences while often disregarding the magnitudes and absolute differences in the effect sizes. This type of reasoning has been shown to be potentially harmful to science. Techniques relying on the visual estimation of the strength of evidence have been recom…
Robust Conditional Independence maps of single-voxel Magnetic Resonance Spectra to elucidate associations between brain tumours and metabolites.
2020
The aim of the paper is two-fold. First, we show that structure finding with the PC algorithm can be inherently unstable and requires further operational constraints in order to consistently obtain models that are faithful to the data. We propose a methodology to stabilise the structure finding process, minimising both false positive and false negative error rates. This is demonstrated with synthetic data. Second, to apply the proposed structure finding methodology to a data set comprising single-voxel Magnetic Resonance Spectra of normal brain and three classes of brain tumours, to elucidate the associations between brain tumour types and a range of observed metabolites that are known to b…
A study on the degree of relationship between two individuals.
2000
The paper studies the likely degree of relationship between two individuals who could possibly be half sibs. The possible common ancestor was dead, which further complicated the problem. The model used was devised by Thompson [in Rao and Chakraborty (eds): Handbook of Statistics, North-Holland, Amsterdam, 1991] and establishes a correspondence between the possible degree of relationship and certain feasible probability distributions on the number of identical by descent genes. Two statistical approaches are considered: the classical one, in which the maximum likelihood estimation for the parameters of Thompson’s model are obtained, and the Bayesian one, in which the test of the hypothesis o…
Robustness of the risk–return relationship in the U.S. stock market
2008
Abstract Using GARCH-in-Mean models, we study the robustness of the risk–return relationship in monthly U.S. stock market returns (1928:1–2004:12) with respect to the specification of the conditional mean equation. The issue is important because in this commonly used framework, unnecessarily including an intercept is known to distort conclusions. The existence of the relationship is relatively robust, but its strength depends on the prior belief concerning the intercept. The latter applies in particular to the first half of the sample, where also the coefficient of the relative risk aversion is smaller and the equity premium greater than in the latter half.
Artificial Reefs in the Gulf of Castellammare (North-West Sicily): A Case Study
2000
Most of the plans for fish stock replenishment recently undertaken in Sicily have focused on the Gulf of Castellammare. Reasons for choosing this biotope for a restocking plan include the size of the Gulf (300 km2), the importance and traditional role of its fisheries and the existence of information describing the local marine environment. The Gulf of Castellammare is the widest bay in Sicily and fishing has always played a major role in the local economy. Today income from fishing complements that from tourism.
Jenis-Jenis Kima dan Kelimpahannya di Perairan Amdui Distrik Batanta Selatan Kabupaten Raja Ampat
2017
Kima merupakan salah satu jenis molusca laut yang banyak ditemukan di perairan Raja Ampat. Hewan ini dilindungi di seluruh dunia termasuk di Indonesia. Penelitian ini dilakukan pada bulan Maret-April 2014, di perairan Amdui yang memiliki ekosistem terumbu karang, dan ditetapkan 3 lokasi pengamatan yaitu: Pulau Ayem, Teluk Sawawris dan Teluk Sawros. Metode yang digunakan pada penelitian ini adalah metode observasi dengan teknik belt transek, dan bertujuan untuk mengetahui jenis dan kelimpahan kima di perairan Amdui. Kima yang ditemukan di perairan laut Kampung Amdui Kabupaten Raja Ampat yaitu 8 jenis terdiri dari T. crocea, T. maxima, T. squamosa, T .gigas, H. porcellanus, H. hippopus, T. te…
Density and distribution patterns of the endangered species Pinna nobilis within the harbour bay of Favignana (Egadi Islands MPA)
2015
The fan shell P. nobilis (Linnaeus, 1758) is the largest marine bivalve in the Mediterranean Sea which acts as ecosystem engineer, offering an adequate substratum to several associated benthic species. P. nobilis is threatened by the reduction and loss of its natural habitat and by increased anthropogenic inputs into coastal waters. The knowledge on the population of this species are scarce, especially as concerns Sicily and its coasts. This study focused on the density of population, spatial distribution, level of burial and orientation of the population of P. nobilis in the harbour area of Favignana island (western coast of Sicily, Italy). The fan shell surveys were carried out by SCUBA d…
Distribution and diversity of fish species exposed to artisanal fishery along the Sudanese Red Sea coast
2019
AbstractThe semi-enclosed Red Sea harbours one of the longest coral-reef ecosystems on the planet. The ≈ 850 km section of the western shore, comprising the coastline of the Red Sea State of the Republic of Sudan, has however been sparsely studied. Sudan’s coral reef fishery provides livelihoods to fishers and business opportunities by means of local and regional trade, however, the knowledge level of the state of the natural resources and the impacts of fisheries are poorly known. Here we report the results from the first three comprehensive fisheries research surveys spanning the entire Sudanese coast in 2012-13, representing a new baseline for the western coast fisheries resources. The s…