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Sobre o emprego e a análise estatística do delineamento em blocos aumentados no melhoramento genético vegetal.; Application and statistical analysis of augmented block design in plant breeding.

Duarte, João Batista
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 19/05/2000 PT
Relevância na Pesquisa
65.78%
A presente pesquisa propôs-se a investigar problemas de ordem estatístico-experimental relacionados à aplicação do delineamento de blocos aumentados, em programas de melhoramento genético vegetal. Nesses desenhos experimentais há duas categorias de tratamentos: as testemunhas (repetidas) e os tratamentos adicionais ou novos (normalmente não repetidos). As primeiras usualmente são cultivares comerciais já recomendados, e os outros, os novos materiais genéticos sob avaliação. Sua relação com os delineamentos de blocos em geral, princípios para a sua aplicação e análise estatística, bem como informações correlatas de outros temas aqui investigados (modelos mistos, componentes de variância e análise espacial de experimentos) foram objetos de revisão no Capítulo 1. O material que fundamentou este trabalho foi um conjunto de 41 ensaios de competição de linhagens de soja (genótipos), em gerações de autofecundação nunca inferiores a F5. Os ensaios, assim delineados, fazem parte do Programa de Melhoramento da Soja desenvolvido pelo Setor de Genética Aplicada às Espécies Autógamas, do Departamento de Genética da ESALQ/USP. Foram escolhidos, preferencialmente, os ensaios que dispunham de mapa de campo completo...

Caracterização de tecidos mamários através de modelos estatísticos utilizando o espalhamento de raios-x".; Breast Tissue Characterization by Statistical Models Using X-Ray Scattering

Cunha, Diego Merigue da
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 24/03/2006 PT
Relevância na Pesquisa
55.77%
Em um exame mamográfico, quando os fótons de raios-X incidem sobre a mama, uma parte destes fótons é transmitida sem ser desviada da trajetória inicial (radiação transmitida primária), permitindo a formação da imagem mamográfica, e outra é dispersa de sua trajetória inicial pelo tecido (radiação espalhada), atuando de forma deletéria na imagem mamográfica. Entretanto, recentes investigações têm demonstrado que a radiação espalhada pode ser útil na caracterização de tecidos. O objetivo deste trabalho é desenvolver um modelo de diagnóstico de alterações no tecido mamário utilizando as informações presentes na distribuição angular da radiação espalhada (perfil de espalhamento). Os perfis de espalhamento de 40 amostras de tecidos mamários foram obtidos utilizando um difractômetro comercial SIEMENS D5005, operando em modo reflexão na energia de 8,04 keV e variando o detector da posição angular de 5º a 150º, correspondendo a um intervalo de x de 0,03Å-1 a 0,62 Å-1. As amostras de tecido foram previamente classificadas histopatologicamente como tecidos normais, fibroadenomas (neoplasias benignas) e diferentes tipos de carcinomas (neoplasias malignas). Neste trabalho, três modelos de diagnóstico baseados na análise estatística dos perfis de espalhamento foram desenvolvidos. O primeiro...

Otimização das colunas de absorção da recuperação de acetona na produção de Filter Tow por meio de estudos fenomenológicos e análise estatística.; Optimization of the absorption columns in the acetone recovery at the Filter Tow production by phenomenological studies and statistical analysis.

Nasser Junior, Roberto
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 13/11/2009 PT
Relevância na Pesquisa
65.76%
A absorção é a etapa determinante da recuperação de acetona no Filter Tow, por reduzir a emissão de acetona e trazer melhorias à economia. Por isso, ela constitui o objeto deste estudo, que inclui desde a revisão dos conceitos fenomenológicos, considerando a escolha do melhor modelo de equilíbrio líquido-vapor, passando pela execução dos balanços coerentes de massa e o estabelecimento da Fotografia da situação original, relatando um caso complexo de transposição de pratos para recheios. Contudo, a operação das colunas de absorção é influenciada por outras variáveis de caráter desconhecido, ruídos em relação à fenomenologia, o que se pretende avaliar, justificando-se desenvolver estudo para avaliar seus efeitos. Com o objetivo geral de otimizar absorção, uma análise estatística foi executada a partir do levantamento de dados operacionais, utilizando todas suas variáveis, sejam as fenomenológicas, como os ruídos, com o objetivo específico de obter modelos empíricos que complementem as simulações fenomenológicas, aumentando sua abrangência. Para a execução da análise estatística, os conjuntos de dados históricos foram levantados e validados pelos balanços coerentes de massa e pela Fotografia...

A statistical analysis of loss factor to determine the energy losses

De Oliveira, M. E.; Boson, D. F A; Padilha-Feltrin, A.
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Conferência ou Objeto de Conferência
ENG
Relevância na Pesquisa
65.69%
Given that the total amount of losses in a distribution system is known, with a reliable methodology for the technical loss calculation, the non-technical losses can be obtained by subtraction. A usual method of calculation technical losses in the electric utilities uses two important factors: load factor and the loss factor. The load factor is usually obtained with energy and demand measurements, whereas, to compute the loss factor it is necessary the learning of demand and energy loss, which are not, in general, prone of direct measurements. In this work, a statistical analysis of this relationship using the curves of a sampling of consumers in a specific company is presented. These curves will be summarized in different bands of coefficient k. Then, it will be possible determine where each group of consumer has its major concentration of points. ©2008 IEEE.

Aplicação das metodologias de analise estatistica e de Analise do Custo do Ciclo de Vida (ACCV) para o estabelecimento de padrões de eficiencia energetica : refrigeradores brasileiros; Application of the methodology of statistical analysis and of life cycle cost analysis (LCCA) to the establishment energy efficiency standards brazilian refrigerators

Herculano Xavier da Silva Junior
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 28/07/2005 PT
Relevância na Pesquisa
55.81%
o objetivo desta dissertação é discutir a aplicação das metodologias de Análise do Custo do Ciclo de Vida (ACCV) e de Análise Estatística como ferramentas para propor padrões de eficiência energética, complementares às etiquetas (selos) voluntárias já existentes, nos refrigeradores brasileiros de uma porta. Um outro objetivo é estudar o papel desses instrumentos (Selos e Padrões de Eficiência Energética) como meios de fornecer subsídios técnicos para o estabelecimento de níveis máximos de consumo de energia elétrica para equipamentos consumidores de eletricidade comercializados no Brasil. As metodologias ACCV e Análise Estatística permitem avaliar os impactos do aumento de eficiência energética nesses equipamentos, resultando em economias (de energia, financeiras, redução na emissão de dióxido de carbono, etc.) importantes para os consumidores e para o País. Os resultados alcançados nesse estudo apresentam importantes dados para subsidiar discussões mais aprofundadas com os fabricantes e governo para estipular padrões mínimos de eficiência energética para os refrigeradores brasileiros. Uma das importantes conclusões é que, apesar de existirem outras metodologias como a Análise Estatística, a ACCV que leva em conta os custos tecnológicos permite que se conheça melhor o mercado (custos...

Statistical analysis of compressive strength of concrete specimens

Aguiar, J. L. Barroso de; Veiga, E.; Oliveira, Pedro
Fonte: Elmaarefa Printing House Publicador: Elmaarefa Printing House
Tipo: Conferência ou Objeto de Conferência
Publicado em //2003 ENG
Relevância na Pesquisa
65.72%
This paper presents the statistical analysis of compressive strength of concrete specimens delivered in a laboratory of Northern of Portugal. Three types of concretes were analyzed defined as C20, C25 and C30. In the study we used the results of three years, 1995 to 1997. The one-sample Kolmogorov-Smirnov Test was used to verify the normal distribution of the strength results. The results presented in this paper are important for predicting the performance of structural elements and for calculating resistance factors for limit state design codes. As concrete is made in majority on site, conformity is more difficult than for other construction materials produced on factories. For the first analysis the concrete applied on the different sites were separated in groups. A total of 82 groups of concrete produced in 20 sites, were analyzed. We verified that in about 32% of the groups the characteristic compressive strength established for the design was not achieved. For the second analysis the total results were considered, without separation by site or by group. When the exigency was classes C20 or C25, the characteristic compressive strength was below the exigency. On the contrary, for the concrete mentioned as C30, the characteristic compressive strength was above the exigency.

Statistical analysis and modeling of optical transport networks; Análise estatística e modelação de redes óticas de transporte

Routray, Sudhir Kumar
Fonte: Universidade de Aveiro Publicador: Universidade de Aveiro
Tipo: Tese de Doutorado
ENG
Relevância na Pesquisa
65.81%
Statistical analysis and modeling of networks is now an integral part of network science and engineering. In case of optical transport networks (OTNs), it can be used for the planning and dimensioning when the complete information is not available or is difficult to process. The core networks around the world today are almost optical and they form the backbone of the Internet. Therefore, the statistical characteristics of these networks must be studied to understand their nature and to estimate their parameters. In science and technology, network analysis and modeling are used for several purposes such as the analysis of their stability, reliability and long term evolution. Knowledge of the statistical models helps in the estimation of several critical parameters of the networks. The work presented in this thesis is focused on the analysis and modeling of link lengths and shortest path lengths in OTNs. The parameters used in the models presented in this thesis can be estimated from the very basic information of the networks such as the coverage area and the number of nodes, both of which can be found from the node locations. These models can be applied to estimate key parameters of the networks. In this thesis, we have shown that the link lengths of the OTNs follow general extreme value distribution. The parameters of the proposed distribution can be estimated from the average link lengths of the networks. We develop expressions for the average link lengths of OTNs which can be estimated with an average error of just 11%. We apply the developed model to estimate link length dependent parameters in OTNs. We show that the shortest path lengths of the OTNs follow Johnson SB distribution. We estimate the parameters of the developed model from the convex area and the number of nodes of the network. We also apply this model to estimate several shortest path-dependent parameters in OTNs.; A análise estatística e modelação de redes é atualmente uma parte integrante da ciência e engenharia de redes. No caso das redes óticas de transporte (OTN)...

A multivariate statistical analysis of the QSAR of 2-(substituted phenyl)indan-1,3-diones with hypolipidemic activity

Silva,Aluizio G. da; Ramos,Mozart N.
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/09/2012 EN
Relevância na Pesquisa
65.72%
Electronic descriptors obtained from AM1 molecular orbital calculations were employed, along with the empirical parameters log P and π, in a multivariate statistical analysis of the quantitative structure-activity relationships (QSAR) in a group of sixteen 2-(substituted phenyl)indan- 1,3-diones possessing hypolipidemic activities. AM1 descriptors were obtained both for the isolated molecule model and, to simulate the solvent effect, for the COSMO model (conductor-like screening model) in our QSAR analysis. From sixteen studied derivatives, three were excluded from the set of molecules used in the model building stage in order to serve as a test set. In general, the results obtained from this test set validated our quantitative models, which were based on linear regressions and principal component analysis (PCA). From these results, new derivatives were predicted to be more potent hypolipidemic agents than the indan-1,3-diones for which experimental activities were determined. For instance, our results suggest that 2-(ortho-hydroxy-phenyl)indan-1,3-dione is a potential candidate for new experimental screening studies for reducing serum cholesterol and triglyceride levels.

Statistical analysis of acoustic emission signals generated during turning of a metal matrix composite

Mukhopadhyay,C. K.; Jayakumar,T.; Raj,Baldev; Venugopal,S.
Fonte: Associação Brasileira de Engenharia e Ciências Mecânicas - ABCM Publicador: Associação Brasileira de Engenharia e Ciências Mecânicas - ABCM
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2012 EN
Relevância na Pesquisa
65.73%
Acoustic emission technique (AET) has been used to monitor the progress of tool wear during turning of silicon carbide (20 wt.%) dispersed Al alloy metal matrix composite. Acoustic emission (AE) signals generated beyond a specific cutting distance increase abruptly. Statistical analysis based on assumed β distribution of AE energy showed that skewness and kurtosis vary with cutting time. Comparison of these results with bparameter of amplitude distribution of AE hits presented in an earlier investigation has shown that while b-parameter is useful for monitoring tool wear up to 0.4 mm, skewness and kurtosis can better monitor the wear beyond that. Uncertainty measurement of AE energy for different cutting distances was determined as per ISO GUM. The combined uncertainty for the measurement of AE energy lies in the range of 0.38 to 1.69, with higher values for the cutting distance between 213.8 mm and 454.5 mm. Different parameters such as skewness and kurtosis of the statistical distribution, b-parameter of amplitude distribution and uncertainties can be used in a complimentary manner for comprehensive evaluation of tool wear.

Application of public-domain statistical analysis software for evaluation and comparison of comet assay data

Verde, Pablo Emílio; Monserrat, Laura Alicia Geracitano; Amado, Lílian Lund; Rosa, Carlos Eduardo da; Bianchini, Adalto; Monserrat, José María
Fonte: Universidade Federal do Rio Grande Publicador: Universidade Federal do Rio Grande
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
55.79%
A novel approach for statistical analysis of comet assay data (i.e.: tail moment) is proposed, employing public-domain statistical software, the R system. The analytical strategy takes into account that the distribution of comet assay data, like the tail moment, is usually skewed and do not follow a normal distribution. Probability distributions used to model comet assay data included: the Weibull, the exponential, the logistic, the normal, the log normal and log-logistic distribution. In this approach it was also considered that heterogeneity observed among experimental units is a random feature of the comet assay data. This statistical model can be characterized with a location parameter mij, a scale parameter r and a between experimental units variability parameter θ. In the logarithmic scale, the parameter mij depends additively on treatment and random effects, as follows: log(mij) = a0 + a1xij + bi, where exp(a0) represents approximately the mean value of the control group, exp(a1) can be interpreted as the relative risk of damage with respect to the control group, xij is an indicator of experimental group and exp(bi) is the individual risk effects assume to follows a Gamma distribution with mean 1 and variance θ. Model selection is based on Akaike’s information criteria (AIC). Real data coming from comet analysis of blood samples taken from the flounder Paralichtys orbignyanus (Teleostei: Paralichtyidae) and from samples of cells suspension obtained from the estuarine polychaeta Laeonereis acuta (Nereididae) were employed. This statistical approach showed that the comet assay data should be analyzed under a modeling framework that take into account the important features of these measurements. Model selection and heterogeneity between experimental units play central points in the analysis of these data.

Everitt, B. S. and Dunn, G. Statistical analysis of medical data: New developments

Solomon, P.
Fonte: International Biometric Soc Publicador: International Biometric Soc
Tipo: Artigo de Revista Científica
Publicado em //2001 EN
Relevância na Pesquisa
65.69%
Book Review: EVERITT, B. S. and DUNN, G. Statistical Analysis of Medical Data: New Developments. Arnold, London, 1998. xi + 340 pp. ?29.99/$45.00. ISBN 0-340-67775-9 (pbk).

The Australasian Resuscitation in Sepsis Evaluation (ARISE) trial statistical analysis plan

Delaney, A.; Peake, S.; Bellomo, R.; Cameron, P.; Holdgate, A.; Howe, B.; Higgins, A.; Presneill, J.; Webb, S.
Fonte: Australasian Academy of Critical Care Medicine Publicador: Australasian Academy of Critical Care Medicine
Tipo: Artigo de Revista Científica
Publicado em //2013 EN
Relevância na Pesquisa
55.8%
The Australasian Resuscitation in Sepsis Evaluation (ARISE) study is an international, multicentre, randomised, controlled trial designed to evaluate the effectiveness of early goal-directed therapy compared with standard care for patients presenting to the emergency department with severe sepsis. In keeping with current practice, and considering aspects of trial design and reporting specific to non-pharmacological interventions, our plan outlines the principles and methods for analysing and reporting the trial results. The document is prepared before completion of recruitment into the ARISE study, without knowledge of the results of the interim analysis conducted by the data safety and monitoring committee and before completion of the two related international studies. Our statistical analysis plan was designed by the ARISE chief investigators, and reviewed and approved by the ARISE steering committee. We reviewed the data collected by the research team as specified in the study protocol and detailed in the study case report form. We describe information related to baseline characteristics, characteristics of delivery of the trial interventions, details of resuscitation, other related therapies and other relevant data with appropriate comparisons between groups. We define the primary...

Australasian Resuscitation In Sepsis Evaluation trial statistical analysis plan

Delaney, A.; Peake, S.; Bellomo, R.; Cameron, P.; Holdgate, A.; Howe, B.; Higgins, A.; Presneill, J.; Webb, S.
Fonte: Blackwell Science Asia Pty Ltd Publicador: Blackwell Science Asia Pty Ltd
Tipo: Artigo de Revista Científica
Publicado em //2013 EN
Relevância na Pesquisa
65.81%
BACKGROUND The Australasian Resuscitation In Sepsis Evaluation (ARISE) study is an international, multicentre, randomised, controlled trial designed to evaluate the effectiveness of early goal-directed therapy compared with standard care for patients presenting to the ED with severe sepsis. OBJECTIVE In keeping with current practice, and taking into considerations aspects of trial design and reporting specific to non-pharmacologic interventions, this document outlines the principles and methods for analysing and reporting the trial results. The document is prepared prior to completion of recruitment into the ARISE study, without knowledge of the results of the interim analysis conducted by the data safety and monitoring committee and prior to completion of the two related international studies. METHODS The statistical analysis plan was designed by the ARISE chief investigators, and reviewed and approved by the ARISE steering committee. The data collected by the research team as specified in the study protocol, and detailed in the study case report form were reviewed. Information related to baseline characteristics, characteristics of delivery of the trial interventions, details of resuscitation and other related therapies, and other relevant data are described with appropriate comparisons between groups. The primary...

Economic and Statistical Analysis of Tourism in Uganda

World Bank Group
Fonte: Washington, DC Publicador: Washington, DC
Tipo: Economic & Sector Work :: Foreign Trade, FDI, and Capital Flows Study; Economic & Sector Work
ENGLISH; EN_US
Relevância na Pesquisa
65.73%
The Ministry of Tourism, Wildlife, and Antiquities (MTWA) instituted a sample survey of tourists exiting Uganda in 2012-the Tourism Expenditure and Motivation Survey (TEMS). This survey collected data on tourist expenditures, duration of stay, tourist activities, sites visited, levels of satisfaction, and suggestions for improvements in the sector. The purpose of this report is to present the results of the economic analysis of tourist expenditures, and the associated statistical analysis, to inform government decisions on how to increase the contribution that tourism makes to the growth of the Ugandan economy. The economic analysis of tourism based on the TEMS survey focuses on the impact of tourist expenditures on the economy. The scope is therefore limited to the impact of tourism exports, but these exports are important contributors to the development of the Ugandan economy, increasing foreign exchange earnings, and improving the balance of payments. The data show that leisure and cultural tourists spend 30 percent to 100 percent more than other types of tourists per visit to Uganda. This substantial difference in spending makes these tourists an attractive target in government efforts to increase the economic contribution of the tourism sector and reinforces the importance of strengthening the marketing of Ugandan tourism. The TEMS survey estimates that roughly 500...

Toward A Common Framework for Statistical Analysis and Development

Imai, Kosuke; King, Gary; Lau, Olivia
Fonte: American Statistical Association Publicador: American Statistical Association
Tipo: Artigo de Revista Científica
EN_US
Relevância na Pesquisa
65.77%
We describe some progress toward a common framework for statistical analysis and software development built on and within the R language, including R's numerous existing packages. The framework we have developed offers a simple unified structure and syntax that can encompass a large fraction of statistical procedures already implemented in R, without requiring any changes in existing approaches. We conjecture that it can be used to encompass and present simply a vast majority of existing statistical methods, regardless of the theory of inference on which they are based, notation with which they were developed, and programming syntax with which they have been implemented. This development enabled us, and should enable others, to design statistical software with a single, simple, and unified user interface that helps overcome the conflicting notation, syntax, jargon, and statistical methods existing across the methods subfields of numerous academic disciplines. The approach also enables one to build a graphical user interface that automatically includes any method encompassed within the framework. We hope that the result of this line of research will greatly reduce the time from the creation of a new statistical innovation to its widespread use by applied researchers whether or not they use or program in R.; Government

Critical analysis of the use of statistical tests in Brazilian publications related to digestive tract surgery

Orso,Ivan Roberto Bonotto; Pereira,Julio C R; D'Albuquerque,Luiz A C; Cecconello,Ivan; Jukemura,José
Fonte: Associação Médica Brasileira Publicador: Associação Médica Brasileira
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/02/2011 EN
Relevância na Pesquisa
55.79%
OBJECTIVE: To evaluate the evolution of scientific papers published on digestive tract surgery in Brazilian journals in 20 years and examine whether the level of evidence in the studies has improved, as well as the incorporation of statistical procedures and their proper application. METHODS: We selected all original articles related to digestive tract surgery published in the years of 1987 and 2007 in 4 leading Brazilian surgical journals. Studies were divided according to the level of evidence (I: prospective, controlled and randomized, II: prospective without control or randomization and III: retrospective) and compared them to assess whether there was an improvement in the level of evidence between these two years surveyed. We also assessed whether there was increased use of analytical statistics and correct application of statistical procedures. RESULTS: Comparing the articles published in 1987 with those of 2007, we observed no improvement with respect to the level of evidence, with more than half of the articles published being case series and retrospective studies (56.14%). There has been a significant increase in the use of analytical statistics (70.4% in 2007 vs. 40% in 1987) in the 20 years, however 16.7% of the studies published in 2007 did not correctly apply or adequately describe the statistical analyses used. CONCLUSION: In this study...

The variation of the fine structure constant: an update of statistical analysis with recent data

Kraiselburd, Lucila; Landau, Susana Judith; Simeone, Claudio Mauricio
Fonte: Edp Sciences S A Publicador: Edp Sciences S A
Tipo: info:eu-repo/semantics/article; info:ar-repo/semantics/artículo; info:eu-repo/semantics/publishedVersion Formato: application/pdf
ENG
Relevância na Pesquisa
65.73%
Aims. We analyze different astronomical data of the variation in the fine structure constant obtained with KECK and VLT to check their consistency.Methods. We test consistency using the Student test and confidence intervals. We split the data sets in smaller intervals and group them by i) redshift and ii) angular position. Another statistical analysis is proposed considering phenomenological models for the variation in alpha. Results. Results show consistency for reduced intervals for each pair of data sets considered and suggest that the variation in alpha is important at higher redshifts.Conclusions. Even though the ?dipole model? proposed by Webb et al. seems to be the most accurate phenomenological model, the statistical analyses indicates that the variation in might be depending both on redshift and angular position.; Fil: Kraiselburd, Lucila. Universidad Nacional de la Plata. Facultad de Cs.astronomicas y Geofisicas. Area Fisica Teorica;; Fil: Landau, Susana Judith.; Fil: Simeone, Claudio Mauricio. Departamento de Física. FCEN. UBA;

Instant Replay: Investigating statistical Analysis in Sports

Sidhu, Gagan
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
55.8%
Technology has had an unquestionable impact on the way people watch sports. Along with this technological evolution has come a higher standard to ensure a good viewing experience for the casual sports fan. It can be argued that the pervasion of statistical analysis in sports serves to satiate the fan's desire for detailed sports statistics. The goal of statistical analysis in sports is a simple one: to eliminate subjective analysis. In this paper, we review previous work that attempts to analyze various aspects in sports by using ideas from Markov Chains, Bayesian Inference and Markov Chain Monte Carlo (MCMC) methods. The unifying goal of these works is to achieve an accurate representation of the player's ability, the sport, or the environmental effects on the player's performance. With the prevalence of cheap computation, it is possible that using techniques in Artificial Intelligence could improve the result of statistical analysis in sport. This is best illustrated when evaluating football using Neuro Dynamic Programming, a Control Theory paradigm heavily based on theory in Stochastic processes. The results from this method suggest that statistical analysis in sports may benefit from using ideas from the area of Control Theory or Machine Learning; Comment: 13 pages

Modeling count data of rare species: some statistical issues

Cunningham, Ross; Lindenmayer, David
Fonte: Ecological Society of America Publicador: Ecological Society of America
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
55.79%
Most species abundance data show that a small number of species contribute the vast majority of individuals to a community. Thus, most taxa in a community are uncommon or rare. Yet such species will frequently be of ecological, conservation, or management interest. Data for uncommon or rare species will be presence/absence data or counts of abundance that contain a greater number of zero observations than would be predicted using standard, unimodal statistical distributions. Such data are generally referred to as zero-inflated data and require specialized methods for statistical analysis. Statistical approaches to modeling zero-inflated data include nonstandard mixture models; two-part, conditional models; and birth process models. In this paper, we briefly summarize two of these methods and illustrate the two-part, conditional approach to the problem of modeling count data with extra zeros. An advantage of this approach includes separate fits and separate interpretations of both components of count data; that is to say, the presence/absence component and the abundance component (given presence) can be analyzed separately. This can be valuable not only for simplicity, but also such a two-step method may assist ecological understanding in cases where the basis for species presence might be separated from the underlying reasons affecting the population size of that species at those sites where it is present. We present two case studies of the application of the two-part conditional model for modeling count data with extra zeros. One deals with modeling relationships between counts of the rare and endangered arboreal marsupial...

Weighting of items in a tutorial performance evaluation instrument: Statistical analysis and results

Lack,Melanie L.; Bruce,Judith C.; Becker,Piet J.
Fonte: Health SA Gesondheid (Online) Publicador: Health SA Gesondheid (Online)
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2009 EN
Relevância na Pesquisa
65.69%
Weighting of items in an evaluation instrument contributes to more meaningful and valid interpretations of student performance in respect of each learning outcome or item being assessed. It follows that the validity of instruments is important for meaningful inferences about students' learning performance, including their performance in tutorial groups. The Delphi technique was used to elicit experts' subjective judgement of the content validity of items in the tutorial performance evaluation instrument in rounds one and two. A sample of eight experts (n = 8) was selected by purposive, maximum variation sampling. In round three Delphi a weighted score was determined for each of the instrument items, subitems and Likert scale points through pairwise comparison by the experts. Mathematical modelling of experts' weighting comparisons, recorded on visual analogue scales, resulted in proportional weights for each item; these weights are expressed as a percentage. The final instrument comprised weighted items measured on a rating scale with points that are not equidistant. A computerised tutorial performance evaluator (TPE) was developed for accurate, economical and efficient calculation of student scores. The purpose of this article is to report on the statistical analysis and results of the weighting of items in an instrument to assess and evaluate baccalaureate nursing students' performance in problem-based learning tutorials.