Estimadores corrigidos para modelos não-lineares generalizados superdispersados

Tese (doutorado) - Universidade Federal de Santa Catarina, Centro Tecnológico. Programa de Pós-Graduação em Engenharia de Produção.A teoria dos modelos lineares e não-lineares da família exponencial vem encontrando espaço cada vez maior entre pesquisadores que querem explorá-la tanto na aplicação quanto na melhoria dos métodos usuais e alternativos. Uma classe mais ampla é a dos modelos lineares e não-lineares generalizados superdispersados, nos quais se modelam os parâmetros da média e dispersão e que, além disso, incorpora a dispersão na função de variância. Essa classe tem sido utilizada de forma expressiva principalmente para dados onde haja superdispersão, isto é, onde a variância real seja maior que a predita pelo modelo. Os estimadores dos parâmetros desses modelos los têm vieses de O(n-1 ) e costumam ser ignorados. Entretanto, para amostras de tamanho moderado a pequeno, esses vieses podem ser significativos, podendo atingir o mesmo valor do respectivo erro-padrão. Dentro desse contexto, é plausível fazer melhorias nos estimadores em áreas de atuação onde nem sempre é possível obter grandes amostras, como, por exemplo, na produção industrial, no controle de qualidade, em segmentos de produção de animais, nas engenharias, na farmacologia, na saúde, entre outras. Neste estudo foram obtidas expressões para o viés de O(n-1 ) para corrigir os estimadores de máxima verossimilhança dos parâmetros dos modelos não-lineares generalizados superdispersados. Para validar essa correção, foram executadas simulações de Monte Carlo e aplicações de dados advindos da área de engenharia da produção. Os resultados mostraram que estimativas de O(n-2 ) devem ser utilizadas nos modelos, principalmente em amostras de tamanho pequeno a moderado, podendo-se evidenciar que, quanto menor o tamanho da amostra, maior a necessidade de se fazerem correções. Em termos práticos, isto é, do ponto de vista econômico e operacional, é altamente positivo, pois o fato de se trabalhar com modelos de maior precisão traz como resultado produtos mais uniformes e, consequentemente, redução significativa de custos. The theory of linear and nonlinear models of the exponential class has been growing among researchers who wish to explore it, either as to the application or as to the improvement of ordinary and alternative methods. One broader class is the overdispersed generalized linear and nonlinear models, in which the mean and dispersion parameters are molded, and the dispersion in function of the variance is also incorporated. This class has been significantly used, mainly for dispersion data, that is, where the real variance is higher than the one previewed by the model. odel. The parameters estimators of these models have O(n-1 ) biases and are commonly overlooked. However, for samples varying from moderate to small size, these biases may be significant, reaching the same value as the respective standard errors. In that context, it is plausible to improve the estimators, in the areas where large samples are not possible to be obtained, such as, in the industrial production, quality control, animal production sector, engineering, pharmacology, health, among others. In this study, expressions for the O(n-1 ) bias were obtained to correct the estimators maximum likelihood of the parameters of generalized overdispersed nonlinear models. In order to validate such correction, Monte Carlo simulations and data applications from the production engineering area were carried out. Results showed that the estimates of O(n-2 ) must be used in the models, mainly in the samples of small and moderate size, making clear that the smaller the size of the sample, the bigger the necessity of correction. In a practical view, that is, from the economical and operational point of view, working with more precise models is very positive, because it results in more uniform products and, consequently, significant reduction of costs

Using a Bayesian change-point statistical model with autoregressive terms to study the monthly number of dispensed asthma medications by public health services

In this paper, it is proposed a Bayesian analysis of a time series in the presence of a random change-point and autoregressive terms. The development of this model was motivated by a data set related to the monthly number of asthma medications dispensed by the public health services of Ribeirão Preto, Southeast Brazil, from 1999 to 2011. A pronounced increase trend has been observed from 1999 to a specific change-point, with a posterior decrease until the end of the series. In order to obtain estimates for the parameters of interest, a Bayesian Markov Chain Monte Carlo (MCMC) simulation procedure using the Gibbs sampler algorithm was developed. The Bayesian model with autoregressive terms of order 1 fits well to the data, allowing to estimate the change-point at July 2007, and probably reflecting the results of the new health policies and previously adopted programs directed toward patients with asthma. The results imply that the present model is useful to analyse the monthly number of dispensed asthma medications and it can be used to describe a broad range of epidemiological time series data where a change-point is present.Peer Reviewe

Using a Bayesian change-point statistical model with autoregressive terms to study the monthly number of dispensed asthma medications by public health services

In this paper, it is proposed a Bayesian analysis of a time series in the presence of a random change-point and autoregressive terms. The development of this model was motivated by a data set related to the monthly number of asthma medications dispensed by the public health services of Ribeirão Preto, Southeast Brazil, from 1999 to 2011. A pronounced increase trend has been observed from 1999 to a specific change-point, with a posterior decrease until the end of the series. In order to obtain estimates for the parameters of interest, a Bayesian Markov Chain Monte Carlo (MCMC) simulation procedure using the Gibbs sampler algorithm was developed. The Bayesian model with autoregressive terms of order 1 fits well to the data, allowing to estimate the change-point at July 2007, and probably reflecting the results of the new health policies and previously adopted programs directed toward patients with asthma. The results imply that the present model is useful to analyse the monthly number of dispensed asthma medications and it can be used to describe a broad range of epidemiological time series data where a change-point is present

Diagnóstico precoce do câncer de mama e colo uterino em mulheres do município de Guarapuava, PR, Brasil

The objective of this study is to identify the frequency in which the early diagnosis of breast and cervical cancer takes place in the municipality of Guarapuava, Paraná. A cross-sectional study with population basis was carried out including 885 women with the minimum age of 18 years old, in the period from October to December of 2006. The sample calculation considered the trust level of 95% and the error margin of 3%. The software Statistica version 7.1 was used for the data analysis, considering the level of significance of 5%. Breast self-examination was performed by 63% of the interviewees and clinical examination by 49%. The mammography was performed by less than one forth of the sample. The prevention of cervical cancer was practiced by most of the women (80%). The conclusion was that the studied women from the sample perform preventive exams of breast cancer with less frequency, when compared to cervical cancer preventive exams.O objetivo desta pesquisa é identificar a freqüência com que é realizado o diagnóstico precoce do câncer de mama e de colo uterino no município de Guarapuava, Paraná. Realizou-se estudo transversal de base populacional, incluindo 885 mulheres com idade mínima de 18 anos, no período de outubro a dezembro de 2006. Considerou-se nível de confiança de 95% e margem de erro de 3% para cálculo amostral. Utilizou-se o software Statistica versão 7.1 para a análise dos dados, considerando nível de significância de 5%. O auto-exame das mamas foi realizado por 63% das entrevistadas e o exame clínico em 49%. A mamografia foi realizada por menos de um quarto da amostra. A prevenção do câncer de colo uterino foi praticada pela maioria das mulheres (80%). Conclui-se que as mulheres da amostra estudada realizam exames preventivos de câncer de mama com menos freqüência, se comparado ao exame preventivo de colo de útero.El objetivo de esta investigación fue identificar la frecuencia en la realización de diagnóstico precoz de cáncer de mama y de cuello uterino en mujeres del municipio de Guarapuava-Paraná-Brasil. Se realizó estudio transversal sobre base poblacional de 885 mujeres con edad mínima de 18 años en el período de octubre a diciembre de 2006. Se consideró un nivel de confianza del 95% un margen de error del 3% para el cálculo de la muestra. Se utilizó el software Statistica versión 7.1 para el análisis de los datos, considerándose un nivel de significatividad de 5%. El autoexamen mamario es realizado por el 63% de las entrevistadas, y el examen clínico por el 49%. Menos de un cuarto de la muestra se efectuó mamografías. La prevención del cáncer de cuello uterino fue practicada por la mayoría de las mujeres (80%). Se concluyó en que las mujeres de la muestra estudiada realizan exámenes preventivos del cáncer de mama con menor prevalencia en comparación al examen preventivo de cáncer de cuello de útero

Using a Bayesian change-point statistical model with autoregressive terms to study the monthly number of dispensed asthma medications by public health services

In this paper, it is proposed a Bayesian analysis of a time series in the presence of a random change-point and autoregressive terms. The development of this model was motivated by a data set related to the monthly number of asthma medications dispensed by the public health services of Ribeirao Preto, Southeast Brazil, from 1999 to 2011. A pronounced increase trend has been observed from 1999 to a specific change-point, with a posterior decrease until the end of the series. In order to obtain estimates for the parameters of interest, a Bayesian Markov Chain Monte Carlo (MCMC) simulation procedure using the Gibbs sampler algorithm was developed. The Bayesian model with autoregressive terms of order 1 fits well to the data, allowing to estimate the change-point at July 2007, and probably reflecting the results of the new health policies and previously adopted programs directed toward patients with asthma. The results imply that the present model is useful to analyse the monthly number of dispensed asthma medications and it can be used to describe a broad range of epidemiological time series data where a change-point is present

Avaliação sorológica, clínica e epidemiológica da toxocaríase em áreas urbanas do sul do Brasil

Toxocariasis is a worldwide public-health problem that poses major risks to children who may accidentally ingest embryonated eggs of Toxocara. The objectives of this study were to investigate the occurrence of anti-Toxocara spp. antibodies in children and adolescents and the variables that may be involved, as well as environmental contamination by Toxocara spp. eggs, in urban recreation areas of north central mesoregion, Paraná State, Brazil. From June 2005 to March 2007. a total of 376 blood samples were collected by the Public Health Service from children and adolescents one to 12 years old, of both genders. Samples were analyzed by the indirect ELISA method for detection of anti-Toxocara antibodies. Serum samples were previously absorbed with Ascaris suum antigens, and considered positive with a reagent reactivity index >;1. Soil samples from all of the public squares and schools located in the four evaluated municipalities that had sand surfaces (n = 19) or lawns (n = 15) were analyzed. Of the 376 serum samples, 194 (51.6%) were positive. The seroprevalence rate was substantially higher among children aging one to five years (p = 0.001) and six to eight years (p = 0.022). The clinical signs and symptoms investigated did not show a statistical difference between seropositive and seronegative individuals (p >; 0.05). In 76.5% of the investigated recreation places, eggs of Toxocara were detected in at least one of the five collected samples. Recreation areas from public schools were 2.8 times more contaminated than from public squares. It is important to institute educational programs to inform families and educators, as well as to improve sanitary control of animals and cleaning of the areas intended for recreation in order to prevent toxocariasis.A toxocaríase é um problema de saúde pública mundial, com maior risco para crianças que podem, acidentalmente, ingerir ovos embrionados de Toxocara spp.. Os objetivos deste estudo foram avaliar a ocorrência de anticorpos anti-Toxocara spp. em crianças e adolecentes e as variáveis que podem estar envolvidas, bem como a contaminação ambiental por ovos de Toxocara spp., em locais de recreação, em áreas urbanas da mesorregião norte central, Paraná, Brasil. De junho de 2005 a março de 2007 foram coletadas 376 amostras de sangue de crianças e adolescentes de um a doze anos, de ambos os sexos, atendidas pelo Sistema Único de Saúde. As amostras foram analisadas pelo método de ELISA indireto para detecção de IgG anti-Toxocara e previamente absorvidas com antígeno de Ascaris suum. Foram consideradas reagentes as amostras com índice de reatividade >; 1. A análise das amostras de areias (n = 19) e gramados (n = 15) de cada município foi realizada em todas as praças e escolas públicas. Das 376 amostras de soro, 194 (51,6%) foram positivas. A taxa de soroprevalência foi substancialmente mais elevada entre as crianças na faixa etária de até um a cinco (p = 0.001) e de seis a oito anos de idade (p = 0,022). Os sinais e sintomas clínicos investigados não mostraram diferenças estatísticas entre soropositivos e soronegativos (p >; 0,05). Em 76,5% dos locais de recreação investigados, ovos de Toxocara foram detectados em pelo menos uma das cinco amostras. Os locais de recreação das escolas públicas estavam 2,8 vezes mais contaminados do que as praças. É importante a realização de programas educativos junto às famílias e educadores, o controle sanitário de animais e a higienização dos locais destinados à recreação para prevenção da toxocaríase

Prevalence of Streptococcus agalactiae colonization in pregnant women from the 18th Health Region of Paraná State

Introduction The aim of this study was to determine the prevalence of GBS colonization in pregnant women in a public health service. Methods A study of 496 pregnant women at 35-37 gestational weeks was conducted from September 2011 to March 2014 in 21 municipalities of the 18th Health Region of Paraná State. Vaginal and anorectal samples of each woman were plated on sheep blood agar, and in HPTH and Todd-Hewitt enrichment broths. Results Of the 496 pregnant women, 141 (28.4%) were positive for GBS based on the combination of the three culture media with vaginal and anorectal samples. The prevalence was 23.7% for vaginal samples and 21.9% for anorectal ones. Among the variables analyzed in this study, only urinary infection was a significant factor (0.026) associated with GBS colonization in women. Conclusions Based on these results, health units should performs universal screening of pregnant women and hospitals should provide adequate prophylaxis, when indicated

Item response theory in the production of indicators of socioeconomic metropolitan region of Maringá, Paraná State, Brazil - doi: 10.4025/actascitechnol.v34i4.10478

This study aimed to identify and produce through models of Item Response Theory (IRT) a socio-economic indicator based in the items observed in 2000 Census, following the methodology by Soares (2005). By the IRT Methodology, this indicator, as a latent variable, is obtained through the construction of specific models and scales, making it possible to measure this variable, which according to Andrade et al. (2000), IRT analyzes each item which compose the measuring instrument. This case consists of binary or dichotomous items, which assess the possession of certain assets of domestic comfort. The characteristics of each item were analyzed, as the ability to discrimination and income necessary for the possession of certain property. It was concluded that with 13 items, a trustworthy questionnaire can be done for the construction of a socioeconomic index of Maringa’s metropolitan region

Mixed models in cerebral ischemia study

The data modeling from longitudinal studies stands out in the current scientific scenario, especially in the areas of health and biological sciences, which induces a correlation between measurements for the same observed unit. Thus, the modeling of the intra-individual dependency is required through the choice of a covariance structure that is able to receive and accommodate the sample variability. However, the lack of methodology for correlated data analysis may result in an increased occurrence of type I or type II errors and underestimate/overestimate the standard errors of the model estimates. In the present study, a Gaussian mixed model was adopted for the variable response latency of an experiment investigating the memory deficits in animals subjected to cerebral ischemia when treated with fish oil (FO). The model parameters estimation was based on maximum likelihood methods. Based on the restricted likelihood ratio test and information criteria, the autoregressive covariance matrix was adopted for errors. The diagnostic analyses for the model were satisfactory, since basic assumptions and results obtained corroborate with biological evidence; that is, the effectiveness of the FO treatment to alleviate the cognitive effects caused by cerebral ischemia was found.