Key technology and multi-directional decomposition method of the causal mediation effect analysis / 四川精神卫生

The purpose of this paper was to introduce five key techniques and the multi-directional decomposition methods of effect components in the analysis of causal mediation effects. The contents of the five key technologies were as follows： ① identification of causal mediation effect； ② regression method of causal mediation effect analysis； ③ maximum likelihood estimation； ④ estimation of total effect and various component effects； ⑤ estimation by bootstrap method. The multi-directional decomposition methods included 3 bidirectional decompositions， 2 three-directional decompositions and 1 four-directional decomposition. Through an example， a causal mediation effect analysis model including covariates and interaction terms was constructed with the help of SAS， bidirectional decomposition， three-directional decomposition and four-directional decomposition were carried out for the total effect in the causal mediation effect analysis， and the output results were explained.

Nigeria's cocoa exports: a gravity model approach / Exportações de cacau da Nigéria: uma abordagem do modelo gravitacional

ABSTRACT: What are the major factors affecting Nigeria's cocoa export flows? In answering this question, the authors suggest a commodity-specific gravity model with three different analytical approaches, (the Heckman Sample Selection Model, the Generalised Least Square, and the Poisson Pseudo Maximum Likelihood), based on a period of 24 years of panel data for Nigeria and it's 36 importing partners to estimate the models. The results showed that GDP, exchange rate policy, WTO, EU, and colonial link are positively associated with the Nigerian cocoa export flows. Further, the negative impact of the GDP per capita, landlocked, distance, AU, and ECOWAS are observed. The need for the expansion of exports to the trading partners, especially the EU members (Netherlands, Germany, France, United Kingdom, Belgium, Spain, etc.), Canada, Malaysia, and the USA is particularly highlighted. These results are important for the formulation of future trade policy that could boost up the Nigerian cocoa exports. This would eventually contribute to the diversification of the Nigerian exports and also enhance the country's foreign earnings.

RESUMO: Quais são os principais fatores que afetam os fluxos de exportação de cacau da Nigéria? Ao responder a esta pergunta, os autores sugerem um modelo de gravidade específica de mercadoria com três abordagens analíticas diferentes (o Modelo de Seleção de Amostras de Heckman, o Mínimo Quadrado Generalizado e a Pseudo Máxima Verossimilhança de Poisson), com base em um período de 24 anos de dados em painel para a Nigéria e seus parceiros importadores para estimar os modelos. Os resultados mostram que o PIB, a política cambial, a OMC, a UE e a ligação colonial estão positivamente associados aos fluxos de exportação de cacau da Nigéria. Além disso, é observado o impacto negativo do PIB per capita, sem litoral, distância, UA e CEDEAO. Destaca-se a necessidade de ampliação das exportações para os parceiros comerciais, especialmente os membros da UE (Holanda, Alemanha, França, Reino Unido, Bélgica, Espanha, etc.), Canadá, Malásia e Estados Unidos. Esses resultados são importantes para a formulação de uma política comercial futura que possa impulsionar as exportações de cacau nigeriano. Isso acabaria por contribuir para a diversificação das exportações nigerianas e também aumentar as receitas externas do país.

Measuring the perception of quality physical education in Latin American professionals / Medindo a percepção de profissionais latino-americanos sobre a qualidade da educação física / Midiendo la percepción de profesionales latinoamericanos acerca de la Calidad de la Educación Física

Abstract An unsteady plan for curriculum development and supportive issues in physical education (PE) has created confusion among professionals. The purpose of this research is to investigate the factors perceived as important in the development of quality physical education (QPE) by professionals in Latin American (LA) countries. A questionnaire consisting of 24 items based on QPE was responded by 468 professionals collected from 6 LA cities. An exploratory factor analysis (EFA) of the 24 items using ML extraction and direct oblimin rotation were applied, and the retained 17 items were clustered in a three factor solution referred to as, Development and Supportive Elements for QPE in School (DSFQPE) (α = .935), Core Value of QPEtabl (CVPE) (α = .890), and Curriculum Arrangement of Physical Activities (CAPA) (α = .850). The retained items indicated excellent properties and the basic framework as perceived by professionals from PE in LA countries as important in the investigation of QPE.

Resumo Um plano instável para o desenvolvimento de currículos e questões de apoio na educação física (PE) criou confusão entre os profissionais. O objetivo desta pesquisa é investigar os fatores percebidos como importantes no desenvolvimento da educação física de qualidade (QPE) por profissionais de países da América Latina (AL). Um questionário composto por 24 itens com base no QPE foi respondido por 468 profissionais coletados em 6 cidades da América Latina. Uma análise fatorial exploratória dos 24 itens usando extração ML e rotação obliminar direta foram aplicados, e os 17 itens retidos foram agrupados em uma solução de três fatores denominada Elementos de Desenvolvimento e Suporte para QPE na Escola (DSFQPE) (α = 0,935), Valor essencial do QPE (CVPE) (α = 0,890) e Arranjo Curricular das Atividades Físicas (CAPA) (α = 0,850). Os itens retidos indicaram propriedades excelentes e o referencial básico percebido pelos profissionais de EF em países da América Latina como importante na investigação do PEQ.

Resumen Un plan inestable para el desarrollo curricular y aspectos de apoyo para la educación física (EF) han creado confusión entre los profesionales. El propósito de esta investigación es investigar los factores percibidos como importantes en el desarrollo de la educación física de calidad (EFC) por profesionales en países de América Latina (AL). Un cuestionario que consta de 24 ítems basados en EFC fue respondido por 468 profesionales recolectados en 6 ciudades de LA. Se aplicó un Análisis factorial exploratorio de los 24 ítems que utilizan extracción ML y rotación oblicua directa, y los 17 ítems retenidos se agruparon en una solución de tres factores denominada Elementos de desarrollo y de apoyo para EFC en la escuela (EDAEFC) (α = 0,935); Valor principal de EFC (CVPE) (α = 0,890) y Arreglo del plan de actividades físicas (CAPA) (α = 0,850). Los ítems retenidos indicaron excelentes propiedades y el marco básico es percibido por los profesionales de EF en los países de AL como importante en la investigación de EFC.

Sequence analysis of psbA-trnH gene in chloroplast of Polygonum multiflorum from different producing areas / 中草药

Objective: The molecular identification method of Polygonum multiflorum from different producing areas was explored by using the sequencing of intergenic region of chloroplast genes psbA-trnH. Methods: A total of 116 samples of P. multiflorum were collected from 15 populations in seven provinces and autonomous regions. The total DNA was extracted and the sequences of psbA-trnH were amplified by PCR. The purified PCR products were sequenced and analyzed by MEGA 6.06 software. Results: The genetic distances among the populations of P.multiflorum are 0.001—0.187. In the maximum likelihood phylogenetic tree, 15 populations of P. multiflorum were clustered into two blanches. Conclusion: The genetic variation of P. multiflorum is significant and the psbA-trnH sequences of P. multiflorum can be used as germplasm source for molecular identification between Deqing regarded as geo-authentic habitat and other producing areas.

Diameter distribution in a Brazilian tropical dry forest domain: predictions for the stand and species

ABSTRACT Currently, there is a lack of studies on the correct utilization of continuous distributions for dry tropical forests. Therefore, this work aims to investigate the diameter structure of a brazilian tropical dry forest and to select suitable continuous distributions by means of statistic tools for the stand and the main species. Two subsets were randomly selected from 40 plots. Diameter at base height was obtained. The following functions were tested: log-normal; gamma; Weibull 2P and Burr. The best fits were selected by Akaike's information validation criterion. Overall, the diameter distribution of the dry tropical forest was better described by negative exponential curves and positive skewness. The forest studied showed diameter distributions with decreasing probability for larger trees. This behavior was observed for both the main species and the stand. The generalization of the function fitted for the main species show that the development of individual models is needed. The Burr function showed good flexibility to describe the diameter structure of the stand and the behavior of Mimosa ophthalmocentra and Bauhinia cheilantha species. For Poincianella bracteosa, Aspidosperma pyrifolium and Myracrodum urundeuva better fitting was obtained with the log-normal function.

The Extended Log-Logistic Distribution: Properties and Application

Abstract We propose a new four-parameter lifetime model, called the extended log-logistic distribution, to generalize the two-parameter log-logistic model. The new model is quite flexible to analyze positive data. We provide some mathematical properties including explicit expressions for the ordinary and incomplete moments, probability weighted moments, mean deviations, quantile function and entropy measure. The estimation of the model parameters is performed by maximum likelihood using the BFGS algorithm. The flexibility of the new model is illustrated by means of an application to a real data set. We hope that the new distribution will serve as an alternative model to other useful distributions for modeling positive real data in many areas.

The Study of Nonparametric Estimate Method for Left Truncated and Right Censored Data / 中国卫生统计

Objective Nonparametric maximum likelihood estimate(NPMLE)and Breslow-Fleming-Harrington estimate(BFH)are extremely sensitive to small risk set for left truncated and right censored data,this study aims to develop estimation methods to improve the estimation accuracy and compare the existing methods.Methods We introduced the NPMLE,weighted NPMLE,conditional NPMLE,BFH and a new weighted BFH estimate.Simulation studies were carried out to compare five methods via the integrated absolute error(IAE) and integrated average width(IAW).Results The IAE of NPMLE,BFH,weighted NPMLE,weighted BFH and conditional NPMLE is ascending in turn;The IAW of weighted BFH is the lowest and NPMLE is the largest,BFH,conditional NPMLE and weighted NPMLE is reversed under different censored rate.Conclusion According to the results of simulation and example,weighted BFH and weighted NPMLE is recommended in turn when the risk set is small.Otherwise,the results of five methods would be consistent.

No le tema a los datos perdidos: enfoques modernos para el manejo de datos perdidos

La mayoría de los datos en ciencias sociales y educación presentan valores perdidos debido al abandono del estudio o la ausencia de respuesta. Los métodos para el manejo de datos perdidos han mejorado dramáticamente en los últimos años, y los programas computacionales ofrecen en la actualidad una variedad de opciones sofisticadas. A pesar de la amplia disponibilidad de métodos considerablemente justificados, muchos investigadores e investigadoras siguen confiando en técnicas viejas de imputación que pueden crear análisis sesgados. Este artículo presenta una introducción conceptual a los patrones de datos perdidos. Seguidamente, se introduce el manejo de datos perdidos y el análisis de los mismos con base en los mecanismos modernos del método de máxima verosimilitud con información completa (FIML, siglas en inglés) y la imputación múltiple (IM). Asimismo, se incluye una introducción a los diseños de datos perdidos así como nuevas herramientas computacionales tales como la función Quark y el paquete semTools. Se espera que este artículo incentive el uso de métodos modernos para el análisis de los datos perdidos.

Most of the social and educational data have missing observations due to either attrition or nonresponse. Missing data methodology has improved dramatically in recent years, and popular computer programs as well as software now offer a variety of sophisticated options. Despite the widespread availability of theoretically justified methods, many researchers still rely on old imputation techniques that can create biased analysis. This article provides conceptual introductions to the patterns of missing data. In line with that, this article introduces how to handle and analyze the missing information based on modern mechanisms of full-information maximum likelihood (FIML) and multiple imputation (MI). An introduction about planned missing designs is also included and new computational tools like Quark function, and semTools package are also mentioned. The authors hope that this paper encourages researchers to implement modern methods for analyzing missing data.

Implication of inverse-probability weighting method in the evaluation of diagnostic test with verification bias / 中华流行病学杂志

To evaluate and adjust the verification bias existed in the screening or diagnostic tests.Inverse-probability weighting method was used to adjust the sensitivity and specificity of the diagnostic tests,with an example of cervical cancer screening used to introduce the Compare Tests package in R software which could be implemented.Sensitivity and specificity calculated from the traditional method and maximum likelihood estimation method were compared to the results from Inverse-probability weighting method in the random-sampled example.The true sensitivity and specificity of the HPV self-sampling test were 83.53％ (95％CI:74.23-89.93) and 85.86％ (95％ CI:84.23-87.36).In the analysis of data with randomly missing verification by gold standard,the sensitivity and specificity calculated by traditional method were 90.48％ (95％CI:80.74-95.56) and 71.96％ (95％CI:68.71-75.00),respectively.Thc adjusted sensitivity and specificity under the use of Inverse-probability weighting method were 82.25％ (95％ CI:63.11-92.62) and 85.80％ (95％ CI:85.09-86.47),respectively,whereas they were 80.13 ％ (95％ CI:66.81-93.46) and 85.80％ (95％ CI:84.20-87.41) under the maximum likelihood estimation method.The inverse-probability weighting method could effectively adjust the scnsitivity and specificity of a diagnostic test when verification bias existed,especially when complex sampling appeared.

Health Input, Technical Efficiency and Health Performance：Based on the Estimation of Stochastic Frontier Analysis Method on Health Input Efficiency / 中国卫生经济

Objective: To support the distribution of health resources in China better. Methods: According to the related data of resident health, health resources and marketing index in China from 2005 to 2010, related conclusion was given by using stochastic frontier analysis and fixed effect panel analysis method to establish the change trend of technical efficiency in different provinces and cities. Results and Conclusion: (1) The distribution of technical efficiency in different provinces and cities are asymmetric and generally low;(2)there are obvious differences of technical efficiency among different areas;(3)government input in medical and health field should be focused on central and western areas.

Medical Insurance Affecting on the Health of the Elderly in China：based on the exmination of limited information of the maximum likelihood method / 中国卫生经济

Objective: Based on overcoming the adverse effect of endogenous problem of causality; to study the effect of health insurance for the health of the elderly. Methods: To apply limited information maximum likelihood method and introduce instrumental variables for two-phase analysis. Results: The more to types of medical insurance participated, the easier the risk of chronic diseases could be reduced, but unfavorable to improve self-reported health. Conclusion: The government should develop social insurance under New Rural Cooperative Medical System, to improve the abilities of the elderly in participating in medical insurance.

An Introduction to Logistic Regression: From Basic Concepts to Interpretation with Particular Attention to Nursing Domain

PURPOSE: The purpose of this article is twofold: 1) introducing logistic regression (LR), a multivariable method for modeling the relationship between multiple independent variables and a categorical dependent variable, and 2) examining use and reporting of LR in the nursing literature. METHODS: Text books on LR and research articles employing LR as main statistical analysis were reviewed. Twenty-three articles published between 2010 and 2011 in the Journal of Korean Academy of Nursing were analyzed for proper use and reporting of LR models. RESULTS: Logistic regression from basic concepts such as odds, odds ratio, logit transformation and logistic curve, assumption, fitting, reporting and interpreting to cautions were presented. Substantial shortcomings were found in both use of LR and reporting of results. For many studies, sample size was not sufficiently large to call into question the accuracy of the regression model. Additionally, only one study reported validation analysis. CONCLUSION: Nursing researchers need to pay greater attention to guidelines concerning the use and reporting of LR models.

Evolutionary histories of expanded peptidase families in Schistosoma mansoni

Schistosoma mansoni is one of the three main causative agents of human schistosomiasis, a major health problem with a vast socio-economic impact. Recent advances in the proteomic analysis of schistosomes have revealed that peptidases are the main virulence factors involved in the pathogenesis of this disease. In this context, evolutionary studies can be applied to identify peptidase families that have been expanded in genomes over time in response to different selection pressures. Using a phylogenomic approach, we searched for expanded endopeptidase families in the S. mansoni predicted proteome with the aim of contributing to the knowledge of such enzymes as potential therapeutic targets. We found three endopeptidase families that comprise leishmanolysins (metallopeptidase M8 family), cercarial elastases (serine peptidase S1 family) and cathepsin D proteins (aspartic peptidase A1 family). Our results suggest that the Schistosoma members of these families originated from successive gene duplication events in the parasite lineage after its diversification from other metazoans. Overall, critical residues are conserved among the duplicated genes/proteins. Furthermore, each protein family displays a distinct evolutionary history. Altogether, this work provides an evolutionary view of three S. mansoni peptidase families, which allows for a deeper understanding of the genomic complexity and lineage-specific adaptations potentially related to the parasitic lifestyle.

La separación en regresión logística, una solución y aplicación / The problem of separation in logistic regression, a solution and an application

La regresión logística es una de las técnicas estadísticas más aplicadas cuando se busca explicar el comportamiento probabilístico de algún fenómeno. Un problema que aparece con frecuencia en estos modelos es la separación en los datos, mostrando los grupos de éxitos separados de los fracasos, lo que impide hallar los estimadores de máxima verosimilitud. OBJETIVO: Presentar una revisión y solución del problema, comparando con otras existentes. METODOLOGIA: Simulación del modelo logístico y estimación del sesgo de los parámetros, usando la solución propuesta con el método clásico. Bayesiano y observaciones ficticias y con el método de Firth. RESULTADOS: Los sesgos encontrados son menores al generar el par de observaciones ficticias con el método Bayesiano. Se muestra un ejemplo sobre la edad de la menarquia. DISCUSION: Se aporta una solución adecuada al problema de la separación usando simulación en un esquema de modelo logístico sencillo. Conclusiones: la generación de observaciones ficticias se recomienda dentro de la región de separación y el mejor método de solución está basado en la teoría bayesiana, donde se logra una convergencia en los parámetros del modelo logístico.

Logistic regression is one of the most used statistical techniques for explaining the probabilistic behavior of a given phenomenon. Data separation is a frequent problem in this model, as successes appear separated from failures and make it impossible to find the maximum likelihood estimators. Objective: to present a revision and a solution to the problem, and to compare it with other solutions. METHODOLOGY: a simulation of the logistic model and an estimation of the parameters' bias using the proposed classical and Bayesian solution with fictitious observations, as well as the Firth method. Results: the bias found is lower when the pair of fictitious observations are generated using the Bayesian method. An example about the age at which menarche occurs is presented. DISCUSSION: an appropriate solution to the problem of separation is provided using a simulation in a simple logistic model. CONCLUSIONS: the generation of fictitious observations within the separation region is recommended, and the best solution method is based on Bayesian theory, which achieves convergence of the parameters of the logistic model.

A clinical gamma camera-based pinhole collimated system for high resolution small animal SPECT imaging

The main objective of the present study was to upgrade a clinical gamma camera to obtain high resolution tomographic images of small animal organs. The system is based on a clinical gamma camera to which we have adapted a special-purpose pinhole collimator and a device for positioning and rotating the target based on a computer-controlled step motor. We developed a software tool to reconstruct the target’s three-dimensional distribution of emission from a set of planar projections, based on the maximum likelihood algorithm. We present details on the hardware and software implementation. We imaged phantoms and heart and kidneys of rats. When using pinhole collimators, the spatial resolution and sensitivity of the imaging system depend on parameters such as the detector-to-collimator and detector-to-target distances and pinhole diameter. In this study, we reached an object voxel size of 0.6 mm and spatial resolution better than 2.4 and 1.7 mm full width at half maximum when 1.5- and 1.0-mm diameter pinholes were used, respectively. Appropriate sensitivity to study the target of interest was attained in both cases. Additionally, we show that as few as 12 projections are sufficient to attain good quality reconstructions, a result that implies a significant reduction of acquisition time and opens the possibility for radiotracer dynamic studies. In conclusion, a high resolution single photon emission computed tomography (SPECT) system was developed using a commercial clinical gamma camera, allowing the acquisition of detailed volumetric images of small animal organs. This type of system has important implications for research areas such as Cardiology, Neurology or Oncology.

Comparação entre métodos de estimação do coeficiente de endogamia com dados de frequências alélicas em uma população diplóide / Comparison among inbreeding coefficient estimation methods in a diploid population with two alleles

Neste trabalho, objetivou-se comparar três estimadores do coeficiente de endogamia, F, em uma população diplóide com dois alelos, utilizando-se dados de frequências alélicas em amostras de indíviduos, com diferentes tamanhos obtidas em populações simuladas, por meio do software SAS. Foi avaliado o estimador de F, obtido pela análise de variância de frequências alélicas, o estimador considerando o método dos momentos e o estimador pelo método da máxima verossimilhança. Os resultados encontrados para a média e variância os estimadores, a partir de 1000 estimativas de F, calculadas para cada tamanho de amostra, mostraram que os três estimadores são tendenciosos. Entretanto, de maneira geral, observou-se que o estimador considerando a análise de variância foi menos tendencioso e apresentou menor variância, quando o coeficiente de endogamia da população foi alto. Para tamanho de amostra superior a 50, os três estimadores tiveram comportamento semelhante, independente da frequência alélica e da endogamia da população.

The present work evaluated the properties of three estimators of the inbreeding coefficient, F, in a diploid population with two alleles, using data of gene frequencies in individuals from random samples obtained from populations simulated through the SAS. We evaluated the estimators of F obtained by variance analysis of allelic frequencies, obtained by moment method, and estimator obtained by maximum likelihood method. The analysis of the means and variances of the estimators, obtained from 1000 estimates of F, calculated for each sample size, demonstrated that the three estimators were biased. However, it was observed that the estimator obtained from univariate analysis was less biased and presented smaller variance, when the inbreeding coefficient in the population was elevated, while for populations with low inbreeding, the variance of the estimator obtained by the multivariate analysis was smaller.

Linkage analysis between dominant and co-dominant makers in full-sib families of out-breeding species

As high-throughput genomic tools, such as the DNA microarray platform, have lead to the development of novel genotyping procedures, such as Diversity Arrays Technology (DArT) and Single Nucleotide Polymorphisms (SNPs), it is likely that, in the future, high density linkage maps will be constructed from both dominant and co-dominant markers. Recently, a strictly genetic approach was described for estimating recombination frequency (r) between co-dominant markers in full-sib families. The complete set of maximum likelihood estimators for r in full-sib families was almost obtained, but unfortunately, one particular configuration involving dominant markers, segregating in a 3:1 ratio and co-dominant markers, was not considered. Here we add nine further estimators to the previously published set, thereby making it possible to cover all combinations of molecular markers with two to four alleles (without epistasis) in a full-sib family. This includes segregation in one or both parents, dominance and all linkage phase configurations.

PENCALC: a program for penetrance estimation in autosomal dominant diseases

We present a computer program developed for estimating penetrance rates in autosomal dominant diseases by means of family kinship and phenotype information contained within the pedigrees. The program also determines the exact 95 percent credibility interval for the penetrance estimate. Both executable (PenCalc for Windows) and web versions (PenCalcWeb) of the software are available. The web version enables further calculations, such as heterozygosity probabilities and assessment of offspring risks for all individuals in the pedigrees. Both programs can be accessed and down-loaded freely at the home-page address http://www.ib.usp.br/~otto/software.htm.

Development of a High Resolution SPECT Detector with Depth-encoding Capability for Multi-energy Imaging: Monte Carlo Simulation / 의학물리

The aim of this work was to establish the methodology for event positioning by measuring depth of interaction (DOI) information and to evaluate the system sensitivity and spatial resolution of the new detector for I-125 and Tc-99m imaging. For this purpose, a Monte Carlo simulation tool, DETECT2000 and GATE were used to model the energy deposition and light distribution in the detector and to validate this approach. Our proposed detector module consists of a monolithic CsI(Tl) crystal with dimensions of 50.0x50.0x3.0 mm3. The results of simulation demonstrated that the resolution is less than 1.5 mm for both I-125 and Tc-99m. The main advantage of the proposed detector module is that by using 3 mm thick CsI(Tl) with maximum-likelihood position-estimation (MLPE) method, high resolution I-125 imaging and high sensitivity Tc-99m imaging are possible. In this paper, we proved that our new detector to be a reliable design as a detector for a multi-energy SPECT.

Generalized lineal models for the analysis of binary data from propagation experiments of Brazilian orchids

This study aimed at applying the generalized linear models (GLM) for the analysis of a germination experiment of Cattleya bicolor in which the response variable was binary. The purpose of this experiment was to assess the effects of the storage temperatures and culture mediums on the seed viability. The analyses of variance was also carried out either with or without the data transformation. All the statistical approaches indicated the importance of the storage temperature on the seed viability. But, the culture media and interaction effects were significant only by the GLM. Based on the GLM, the seeds stored at 10°C increased viability, in which the coconut medium achieved the best performance. The results emphasized the importance of adopting the GLM to improve the reliability in many situations where the response variable followed a non-normal distribution.

A técnica de propagação in vitro é considerada efetiva para fins comerciais e de conservação de orquídeas. A metodologia de modelos lineares generalizados (MLG) foi usada para analisar um experimento de germinação de Cattleya bicolor. O propósito do experimento foi avaliar os efeitos da temperatura de armazenamento e dos meios de cultivo sobre a germinação, cuja resposta foi considerada binária. Análise convencional com ou sem transformação de dados foram também realizados. Todas as abordagens estatísticas indicaram a importância da temperatura sobre a viabilidade das sementes. Entretanto, os efeitos de meios de cultivo e interação foram significativos apenas para MLG. As sementes armazenadas a 10°C incrementaram sua viabilidade, onde o meio a base de coco atingiu o melhor desempenho. Os resultados enfatizam a importância de adotar MLG, para melhorar a confiabilidade em situações onde a variável resposta segue uma distribuição distinta à normal.