10 research outputs found
Statistical modelling of space weather extremes and process monitoring of rates and proportions
The first part of this work has been motivated by a multivariate space weather dataset. When the Sun releases high-energy particles into space due to a solar explosion, we experience magnetic storms, that once reaching Earth can last hours or days. Although solar flares emmited by the Sun cannot cause any harm to humans on Earth, if they are too severe they can damage machinery and techonology, such as satellites and radio communication. Thus, the modelling of extreme solar activity is important so we can be prepared for undesireable extreme events. Extreme value analysis can help professionals to understand the risks that severe geomagnetic field fluctuations can pose to Earth. For example, we can characterise the tail of the distribution of geomagnetic disturbances and the probability of extreme events. Hence, we perform a pairwise analysis for modelling the extremes of multiple bivariate processes of geomagnetic activity considering two copula models. The aim is to model the joint extremal probability and depict the pairwise extremal dependence structure between pairs of sites in two regions in Europe. The results show that the dependence structure differs in Northern and Southern Europe and that the dependence weakens as the distance increases. The second part of this work proposes a control chart for detecting small shifts in the mean of a double-bounded process, such as fractions or proportions, in the presence of control variables. For this purpose, we consider the cumulative sum control chart applied to different residuals of the beta regression model. We conduct an extensive Monte Carlo simulation study to evaluate and compare the performance of the proposed control chart with two other control charts in the literature in terms of run length analysis. The numerical results show that the proposed control chart is more sensitive to changes in the process than its competitors and that the quantile residual is the most suitable residual to be used in our proposal. Finally, based on the quantile residual, we present and discuss applications to real and simulated data to show the applicability of the proposed control chart
AVALIAĂĂO DA OCORRĂNCIA DE ESTRO E DESENVOLVIMENTO FOLICULAR EM FĂMEAS SUĂNAS NA LACTAĂĂO COM MANEJO DE DESMAME DE 28 DIAS
O desmame de fĂȘmeas suĂnas Ă© realizado na grande maioria aos 21 dias de lactação, contudo, uma grande discussĂŁo acerca da mudança de manejo de 21 para 28 dias, sem ocorrĂȘncia da manifestação do estro durante a lactação e interferĂȘncia no intervalo desmame cio (IDC) vem sendo discutida. Foram avaliadas 114 fĂȘmeas suĂnas de duas granjas diferentes, quanto a manifestação de estro pelo reflexo de tolerĂąncia ao homem (RTH) e desenvolvimento folicular por ultrassonografia. Os resultados mostraram que nĂŁo houve ocorrĂȘncia de estro durante a lactação no perĂodo de 28 dias e nenhuma interferĂȘncia no IDC em 100% das fĂȘmeas avaliadas
Planos Municipais de SaĂșde do Estado do Tocantins: uma anĂĄlise com foco no enfrentamento da obesidade
This documentary analysis evaluated the scope of addressing obesity in the Municipal Health Plans (PMS) in the state of Tocantins, Brazil, since the growing prevalence of obesity in Brazil should put its confrontation at the center of public health action and management instruments. To analyze the PMS performance from 2018 to 2021 in the 139 municipalities of this state, 17 terms related to obesity were selected and had their frequency and context in the PMS verified. Of the existing 139 PMS, 129 (92.8%) were evaluated. âHealth academyâ and âSISVANâ were the most frequent terms used, whereas âobesityâ appeared in only 28% of the plans, totaling 71 mentions. Of these, only 32.4% were directly related to combating the disease, mainly in the health regions of Bico do Papagaio and MĂ©dio Norte Araguaia. Relevant contexts for addressing obesity included the characterization of the epidemiological profile, tables of action goals, and indicators. PMSâs role in combating obesity is absent in more than 70% of municipalities in Tocantins, which points to the urgent inclusion of this disease within the management instruments.O objetivo deste estudo foi avaliar a abrangĂȘncia do enfrentamento da obesidade nos Planos Municipais de SaĂșde (PMS) do Estado do Tocantins, dado que, diante da crescente prevalĂȘncia da obesidade no Brasil, seu enfrentamento deveria estar no foco de ação da saĂșde pĂșblica e previsto nos instrumentos de gestĂŁo. Trata-se de um estudo qualitativo, com anĂĄlise documental, que analisou os PMS no perĂodo de vigĂȘncia de 2018 a 2021 nos 139 municĂpios desse estado. Foram selecionados dezessete termos relacionados Ă obesidade e verificada a frequĂȘncia e contexto nos PMS. Do total de 139 PMS, foram avaliados 129 (92,8%). Os termos âacademia da saĂșdeâ e âSisvanâ foram os mais frequentes, e âobesidadeâ apareceu em apenas 28% dos planos, totalizando 71 citaçÔes. Destas, somente 32,4% relacionavam-se diretamente com o enfrentamento da doença, com destaque nas regiĂ”es de saĂșde Bico do Papagaio e MĂ©dio Norte Araguaia. Os contextos relevantes de abordagem da obesidade mais frequentes foram a caracterização da situação epidemiolĂłgica, quadros de metas de açÔes e indicadores. Concluiu-se que o enfrentamento da obesidade pactuado nos PMS estĂĄ ausente em mais de 70% dos municĂpios do Tocantins, e que açÔes de direcionamento para inclusĂŁo dessa doença dentro dos instrumentos de gestĂŁo sĂŁo urgentes
Biochemical quality of cowpea beans grown under water-deficit maintained with hydrogel
Investigations related to the effects of the hydrogel use in a water-deficit conditions on the biochemical composition of the harvested products are scarce. The aim of this study was to verify the influence of hydrogel on the biochemical response of cowpea beans produced under water-deficit in southern Tocantins. The experiment was a randomized complete block design with four replications. The treatments were obtained in a 2x5 factorial scheme, being: two sources of hydrogel (Hydroplan-EB HyC and Polim-Agri PP) and five concentrations (0, 5, 10, 15, and 20kg ha-1). After harvesting, the grains of cowpea, BRS Vinagre cultivar, were ground and chemically analyzed. The oil content of the seeds agreed with the reference values. The use of Polim-Agri PP promoted the best levels of amino acids (0.38mg g-1) and proteins (243.22mg g-1) of the grains. The carbohydrate content of them (ÈČ= 81.44mg g-1) was better using Hydroplan-EB HyC, regardless of the concentration applied. The application of 6.28kg ha-1 of Polim-Agri PP provided the highest starch content (842g mg-1). The use of hydrogel improves the biochemical quality of cowpea beans produced under water deficit in southern Tocantins
Kumaraswamy regression model with Aranda-Ordaz link function
In this work, we introduce a regression model for double-bounded variables in the interval (0, 1) following a Kumaraswamy distribution. The model resembles a generalized linear model, in which the responseâs median is modeled by a regression structure through the asymmetric Aranda-Ordaz parametric link function. We consider the maximum likelihood approach to estimate the regression and the link function parameters altogether. We study large sample properties of the proposed maximum likelihood approach, presenting closed-form expressions for the score vector as well as the observed and Fisher information matrices. We briefly present and discuss some diagnostic tools. We provide numeric evaluation of the finite sample inferences to show the performance of the estimators. Finally, to exemplify the usefulness of the methodology, we present and explore an empirical application
Improved testing inferences for beta regressions with parametric mean link function
Beta regressions are widely used for modeling random variables that assume values in the standard unit interval, (0, 1), such as rates, proportions, and income concentration indices. Parameter estimation is typically performed via maximum likelihood, and hypothesis testing inferences on the model parameters are commonly performed using the likelihood ratio test. Such a test, however, may deliver inaccurate inferences when the sample size is small. It is thus important to develop alternative testing procedures that are more accurate when the sample contains only few observations. In this paper, we consider the beta regression model with parametric mean link function and derive two modified likelihood ratio test statistics for that class of models. We provide simulation evidence that shows that the new tests usually outperform the standard likelihood ratio test in samples of small to moderate sizes. We also present and discuss two empirical applications
Residualâbased CUSUM beta regression control chart for monitoring doubleâbounded processes
This paper proposes a control chart useful for detecting small shifts in the mean of a double-bounded process, such as fractions and proportions, in the presence of control variables. For this purpose, we consider the cumulative sum (CUSUM) control chart applied to different residuals of the beta regression model. We conduct an extensive Monte Carlo simulation study to evaluate and compare the performance of the proposed control chart with two other control charts in the literature in terms of run length analysis. The numerical results show that the proposed control chart is more sensitive to detect changes in the process than its competitors and that the quantile residual is the most suitable residual to be used in our proposal. Finally, based on the quantile residual, we present and discuss applications to real and simulated data to show the applicability of the proposed control chart