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Bayesian Statistics (bayesian + statistics)
Selected AbstractsBayesian Core: A Practical Approach to Computational Bayesian Statistics by J. M. MARIN and C. P. ROBERTBIOMETRICS, Issue 3 2007Lawrence Joseph No abstract is available for this article. [source] Case Studies in Bayesian Statistics (Volume IV).BIOMETRICS, Issue 1 2004U. Mansmann No abstract is available for this article. [source] Evidence-based guidelines to optimize the selection of antibody panels in cytopathology: Pleural effusions with malignant epithelioid cellsDIAGNOSTIC CYTOPATHOLOGY, Issue 1 2010Danielle E. Westfall M.D. Abstract There is no established methodology to help select cost effective antibody panels. We used Bayesian statistics and an evidence-based pathology (EBP) approach to retrospectively review the use of immunohistochemistry (IHC) in 153 consecutive pleural effusions evaluated in our laboratory from 2005,2007 for the differential diagnosis of malignant mesothelial cells versus carcinoma cells and to estimate the likely site of origin of a carcinoma. The results in this "training" set were used to design antibody panels and test their clinical applicability on a "test set" of 44 pleural effusions collected in early 2008. Cytopathologists had used 6 ± 4.5 IHC tests per case for the diagnosis of malignant mesothelioma (n = 9) and carcinomas of lung (n = 60), breast (n = 47), Müllerian (n = 25), and other origins in the "training set". The sensitivity and specificity of pleural cytology using all these IHC tests were 32% and 95%, respectively. Sensitivity, specificity and post-test odds (PTO) of a positive IHC result were calculated for each antibody and by the following classes: malignant mesothelial cells and carcinoma cells by primary site of origin. The antibodies that provided the best PTO to diagnose the most prevalent tumors in our population were included in diagnostic panels for male (calretinin, TTF-1, PSA and CDX-2) and female (calretinin, TTF-1, ER and CA125) patients. These panels provided 100% specificity and 77% and 50% sensitivity, respectively, for the pleural effusions from female and male patients in the "test set." The use of an EBP approach for test selection in cytopathology is discussed. Diagn. Cytopathol. 2010. © 2009 Wiley-Liss, Inc. [source] A novel genealogical approach to neutral biodiversity theoryECOLOGY LETTERS, Issue 3 2004Rampal S. Etienne Abstract Current neutral theory in community ecology views local biodiversity as a result of the interplay between speciation, extinction and immigration. Simulations and a mean-field approximation have been used to study this neutral theory. As simulations have limitations of convergence and the mean-field approximation ignores dependencies between species' abundances when applied to species-abundance data, there is still no final conclusion whether the neutral theory or the traditional lognormal model describes community structure best. We present a novel analytical framework, based on the genealogy of individuals in the local community, to overcome the problems of previous approaches, and show, using Bayesian statistics, that the lognormal model provides a slightly better fit to the species-abundance distribution of a much-discussed tropical tree community. A key feature of our approach is that it shows the tight link between genetic and species diversity, which creates important perspectives to future integration of evolutionary and community ecological theory. [source] Competitive On-line StatisticsINTERNATIONAL STATISTICAL REVIEW, Issue 2 2001Volodya Vovk Summary A radically new approach to statistical modelling, which combines mathematical techniques of Bayesian statistics with the philosophy of the theory of competitive on-line algorithms, has arisen over the last decade in computer science (to a large degree, under the influence of Dawid's prequential statistics). In this approach, which we call "competitive on-line statistics", it is not assumed that data are generated by some stochastic mechanism; the bounds derived for the performance of competitive on-line statistical procedures are guaranteed to hold (and not just hold with high probability or on the average). This paper reviews some results in this area; the new material in it includes the proofs for the performance of the Aggregating Algorithm in the problem of linear regression with square loss. Résumé Cet article décrit une approch nouvelle à modelage statistique combinant les techniques mathematiques de statistique Bayesienne avec la philosophie de la theorie de algorithmes compétitives en ligne. Dans cette approche, qui émergeait durant le décennie derniére dans I'informatique, on ne suppose pas que les données sont produites par une mécanaisme stochastique; au lieu de cela, il est prouvé que les procédures statistiques compétitives en ligne atteignent toujours (et non, par exemple, avechaute probabilite) quelque but desirable (explicitant la bonne performance sur les données réeles). Cet article pass en revue des plusieurs résultats dans cette domaine; son matériel neuf comprend les preuves pour la performance de le àlgorithme agrégent dans le probléme de la régression linégression linéaire avec la perte carrée. [source] Bayeswatch: an overview of Bayesian statisticsJOURNAL OF EVALUATION IN CLINICAL PRACTICE, Issue 2 2002Peter C. Austin PhD Abstract Increasingly, clinical research is evaluated on the quality of its statistical analysis. Traditionally, statistical analyses in clinical research have been carried out from a ,frequentist' perspective. The presence of an alternative paradigm , the Bayesian paradigm , has been relatively unknown in clinical research until recently. There is currently a growing interest in the use of Bayesian statistics in health care research. This is due both to a growing realization of the limitations of frequentist methods and to the ability of Bayesian methods explicitly to incorporate prior expert knowledge and belief into the analyses. This is in contrast to frequentist methods, where prior experience and beliefs tend to be incorporated into the analyses in an ad hoc fashion. This paper outlines the frequentist and Bayesian paradigms. Acute myocardial infarction mortality data are then analysed from both a Bayesian and a frequentist perspective. In some analyses, the two methods are seen to produce comparable results; in others, they produce different results. It is noted that in this example, there are clinically relevant questions that are more easily addressed from a Bayesian perspective. Finally, areas in clinical research where Bayesian ideas are increasingly common are highlighted. [source] Bayesian statistics in medical research: an intuitive alternative to conventional data analysisJOURNAL OF EVALUATION IN CLINICAL PRACTICE, Issue 2 2000AStat, Lyle C. Gurrin BSc (Hons) Summary Statistical analysis of both experimental and observational data is central to medical research. Unfortunately, the process of conventional statistical analysis is poorly understood by many medical scientists. This is due, in part, to the counter-intuitive nature of the basic tools of traditional (frequency-based) statistical inference. For example, the proper definition of a conventional 95% confidence interval is quite confusing. It is based upon the imaginary results of a series of hypothetical repetitions of the data generation process and subsequent analysis. Not surprisingly, this formal definition is often ignored and a 95% confidence interval is widely taken to represent a range of values that is associated with a 95% probability of containing the true value of the parameter being estimated. Working within the traditional framework of frequency-based statistics, this interpretation is fundamentally incorrect. It is perfectly valid, however, if one works within the framework of Bayesian statistics and assumes a ,prior distribution' that is uniform on the scale of the main outcome variable. This reflects a limited equivalence between conventional and Bayesian statistics that can be used to facilitate a simple Bayesian interpretation based on the results of a standard analysis. Such inferences provide direct and understandable answers to many important types of question in medical research. For example, they can be used to assist decision making based upon studies with unavoidably low statistical power, where non-significant results are all too often, and wrongly, interpreted as implying ,no effect'. They can also be used to overcome the confusion that can result when statistically significant effects are too small to be clinically relevant. This paper describes the theoretical basis of the Bayesian-based approach and illustrates its application with a practical example that investigates the prevalence of major cardiac defects in a cohort of children born using the assisted reproduction technique known as ICSI (intracytoplasmic sperm injection). [source] A Bayesian Approach to Age Estimation in Modern Americans from the Clavicle,JOURNAL OF FORENSIC SCIENCES, Issue 3 2010Natalie Langley-Shirley Ph.D. Abstract:, Clavicles from 1289 individuals from cohorts spanning the 20th century were scored with two scoring systems. Transition analysis and Bayesian statistics were used to obtain robust age ranges that are less sensitive to the effects of age mimicry and developmental outliers than age ranges obtained using a percentile approach. Observer error tests showed that a simple three-phase scoring system proved the least subjective, while retaining accuracy levels. Additionally, significant sexual dimorphism was detected in the onset of fusion, with women commencing fusion at least a year earlier than men (women transition to fusion at approximately 15 years of age and men at 16 years). Significant secular trends were apparent in the onset of skeletal maturation, with modern Americans transitioning to fusion approximately 4 years earlier than early 20th century Americans and 3.5 years earlier than Korean War era Americans. These results underscore the importance of using modern standards to estimate age in modern individuals. [source] Constraining the age of Lateglacial and early Holocene pollen zones and tephra horizons in southern Sweden with Bayesian probability methods,JOURNAL OF QUATERNARY SCIENCE, Issue 4 2006B. Wohlfarth Abstract The sediment sequence from Hässeldala port in southeastern Sweden provides a unique Lateglacial/early Holocene record that contains five different tephra layers. Three of these have been geochemically identified as the Borrobol Tephra, the Hässeldalen Tephra and the 10-ka Askja Tephra. Twenty-eight high-resolution 14C measurements have been obtained and three different age models based on Bayesian statistics are employed to provide age estimates for the five different tephra layers. The chrono- and pollen stratigraphic framework supports the stratigraphic position of the Borrobol Tephra as found in Sweden at the very end of the Older Dryas pollen zone and provides the first age estimates for the Askja and Hässeldalen tephras. Our results, however, highlight the limitations that arise in attempting to establish a robust, chronologically independent lacustrine sequence that can be correlated in great detail to ice core or marine records. Radiocarbon samples are prone to error and sedimentation rates in lake basins may vary considerably due to a number of factors. Any type of valid and ,realistic' age model, therefore, has to take these limitations into account and needs to include this information in its prior assumptions. As a result, the age ranges for the specific horizons at Hässeldala port are large and calendar year estimates differ according to the assumptions of the age-model. Not only do these results provide a cautionary note for over-dependence on one age-model for the derivation of age estimates for specific horizons, but they also demonstrate that precise correlations to other palaeoarchives to detect leads or lags is problematic. Given the uncertainties associated with establishing age,depth models for sedimentary sequences spanning the Lateglacial period, however, this exercise employing Bayesian probability methods represents the best possible approach and provides the most statistically significant age estimates for the pollen zone boundaries and tephra horizons. Copyright © 2006 John Wiley & Sons, Ltd. [source] Darwin, Galton and the Statistical EnlightenmentJOURNAL OF THE ROYAL STATISTICAL SOCIETY: SERIES A (STATISTICS IN SOCIETY), Issue 3 2010Stephen M. Stigler Summary., On September 10th, 1885, Francis Galton ushered in a new era of Statistical Enlightenment with an address to the British Association for the Advancement of Science in Aberdeen. In the process of solving a puzzle that had lain dormant in Darwin's Origin of Species, Galton introduced multivariate analysis and paved the way towards modern Bayesian statistics. The background to this work is recounted, including the recognition of a failed attempt by Galton in 1877 as providing the first use of a rejection sampling algorithm for the simulation of a posterior distribution, and the first appearance of a proper Bayesian analysis for the normal distribution. [source] Correlated projected properties of some triaxial mass models: implications for their intrinsic shapesMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2001Parijat Thakur The projected properties of some triaxial mass models are studied. The models are flattened versions of a set of spherical models. They are constructed by addition of two spherical harmonic terms to a spherical model. The projected properties exhibit strong correlations, when a model with a given set of intrinsic parameters is viewed in all possible orientations. The correlation plots appear to carry signatures of the intrinsic shape of the mass model. Rigorous shape estimates, using Bayesian statistics, yield satisfactory results for the test cases. [source] Advanced Statistical Analysis as a Novel Tool to Pneumatic Conveying Monitoring and Control Strategy DevelopmentPARTICLE & PARTICLE SYSTEMS CHARACTERIZATION, Issue 3-4 2006Andrzej Romanowski Abstract Behaviour of powder flow in pneumatic conveying has been investigated for many years, though it still remains a challenging task both practically and theoretically, especially when considering monitoring and control issues. Better understanding of the gas-solids flow structures can be beneficial for the design and operation of pneumatic transport installations. This paper covers a novel approach for providing the quantitative description in terms of parameter values useful for monitoring and control of this process with the use of Electrical Capacitance Tomography (ECT). The use of Bayesian statistics for analysis of ECT data allows the direct estimation of control parameters. This paper presents how this characteristic parameters estimation can be accomplished without the need for reconstruction and image post processing, which was a classical endeavour whenever tomography was applied. It is achieved using a ,high-level' statistical Bayesian modelling combined with a Markov chain Monte Carlo (MCMC) sampling algorithm. Advanced statistics is applied to data analysis for measurements coming from the part of phenomena present in the horizontal section of pneumatic conveyor during slug formation. [source] Application of a Bayesian Approach to the Tomographic Analysis of Hopper FlowPARTICLE & PARTICLE SYSTEMS CHARACTERIZATION, Issue 4 2005Krzysztof Grudzien Abstract This paper presents a new approach to the analysis of data on powder flow from electrical capacitance tomography (ECT) using probability modelling and Bayesian statistics. The methodology is illustrated for powder flow in a hopper. The purpose, and special features, of this approach is that ,high-level' statistical Bayesian modelling combined with a Markov chain Monte Carlo (MCMC) sampling algorithm allows direct estimation of control parameters of industrial processes in contrast to usually applied ,low-level', pixel-based methods of data analysis. This enables reliable recognition of key process features in a quantitative manner. The main difficulty when investigating hopper flow with ECT is due to the need to measure small differences in particle packing density. The MCMC protocol enables more robust identification of the responses of such complex systems. This paper demonstrates the feasibility of the approach for a simple case of particulate material flow during discharging of a hopper. It is concluded that these approaches can offer significant advantages for the analysis and control of some industrial powder and other multi-phase flow processes. [source] Statistical basis for positive identification in forensic anthropologyAMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 1 2006Dawnie Wolfe Steadman Abstract Forensic scientists are often expected to present the likelihood of DNA identifications in US courts based on comparative population data, yet forensic anthropologists tend not to quantify the strength of an osteological identification. Because forensic anthropologists are trained first and foremost as physical anthropologists, they emphasize estimation problems at the expense of evidentiary problems, but this approach must be reexamined. In this paper, the statistical bases for presenting osteological and dental evidence are outlined, using a forensic case as a motivating example. A brief overview of Bayesian statistics is provided, and methods to calculate likelihood ratios for five aspects of the biological profile are demonstrated. This paper emphasizes the definition of appropriate reference samples and of the "population at large," and points out the conceptual differences between them. Several databases are introduced for both reference information and to characterize the "population at large," and new data are compiled to calculate the frequency of specific characters, such as age or fractures, within the "population at large." Despite small individual likelihood ratios for age, sex, and stature in the case example, the power of this approach is that, assuming each likelihood ratio is independent, the product rule can be applied. In this particular example, it is over three million times more likely to obtain the observed osteological and dental data if the identification is correct than if the identification is incorrect. This likelihood ratio is a convincing statistic that can support the forensic anthropologist's opinion on personal identity in court. Am J Phys Anthropol, 2006. © 2006 Wiley-Liss, Inc. [source] An efficient computational approach for prior sensitivity analysis and cross-validationTHE CANADIAN JOURNAL OF STATISTICS, Issue 1 2010Luke Bornn Abstract Prior sensitivity analysis and cross-validation are important tools in Bayesian statistics. However, due to the computational expense of implementing existing methods, these techniques are rarely used. In this paper, the authors show how it is possible to use sequential Monte Carlo methods to create an efficient and automated algorithm to perform these tasks. They apply the algorithm to the computation of regularization path plots and to assess the sensitivity of the tuning parameter in g -prior model selection. They then demonstrate the algorithm in a cross-validation context and use it to select the shrinkage parameter in Bayesian regression. The Canadian Journal of Statistics 38:47,64; 2010 © 2010 Statistical Society of Canada La sensibilité à la loi a priori et la validation croisée sont des outils importants des statistiques bayésiennes. Toutefois, ces techniques sont rarement utilisées en pratique car les méthodes disponibles pour les implémenter sont numériquement très coûteuses. Dans ce papier, les auteurs montrent comment il est possible d'utiliser les méthodes de Monte Carlo séquentielles pour obtenir un algorithme efficace et automatique pour implémenter ces techniques. Ils appliquent cet algorithme au calcul des chemins de régularisation pour un problème de régression et à la sensibilité du paramètre de la loi a priori de Zellner pour un problème de sélection de variables. Ils appliquent ensuite cet algorithme pour la validation croisée et l'utilisent afin de sélectionner le paramètre de régularisation dans un problème de régression bayésienne. La revue canadienne de statistique 38: 47,64; 2010 © 2010 Société statistique du Canada [source] | ||||||||||||||||