Levene tests of homogeneity of variance for general block and treatment designs

This article develops a weighted least squares version of Levene's test of homogeneity of variance for a general design, available both for univariate and multivariate situations. When the design is balanced, the univariate and two common multivariate test statistics turn out to be proportional to the corresponding ordinary least squares test statistics obtained from an analysis of variance of the absolute values of the standardized mean-based residuals from the original analysis of the data. The constant of proportionality is simply a design-dependent multiplier (which does not necessarily tend to unity). Explicit results are presented for randomized block and Latin square designs and are illustrated for factorial treatment designs and split-plot experiments. The distribution of the univariate test statistic is close to a standard F-distribution, although it can be slightly underdispersed. For a complex design, the test assesses homogeneity of variance across blocks, treatments, or treatment factors and offers an objective interpretation of residual plot.

Transações com partes relacionadas : determinantes e impactos no desempenho das empresas

A literatura internacional que analisa os fatores impactantes das transações com partes relacionadas concentra-se no Reino Unido, nos EUA e no continente asiático, sendo o Brasil um ambiente pouco investigado. Esta pesquisa tem por objetivo investigar tanto os fatores impactantes dos contratos com partes relacionadas, quanto o impacto dessas transações no desempenho das empresas brasileiras. Estudos recentes que investigaram as determinantes das transações com partes relacionadas (TPRs), assim como seus impactos no desempenho das empresas, levaram em consideração as vertentes apresentadas por Gordon, Henry e Palia (2004): (a) de conflitos de interesses, as quais apoiam a visão de que as TPRs são danosas para os acionistas minoritários, implicando expropriação da riqueza deles, por parte dos controladores (acionistas majoritários); e (b) transações eficientes que podem ser benéficas às empresas, atendendo, desse modo, aos objetivos econômicos subjacentes delas. Esta pesquisa apoia-se na vertente de conflito de interesses, com base na teoria da agência e no fato de que o cenário brasileiro apresenta ter como característica uma estrutura de propriedade concentrada e ser um país emergente com ambiente legal caracterizado pela baixa proteção aos acionistas minoritários. Para operacionalizar a pesquisa, utilizou-se uma amostra inicial composta de 70 empresas com ações listadas na BM&FBovespa, observando o período de 2010 a 2012. Os contratos relacionados foram identificados e quantificados de duas formas, de acordo com a metodologia aplicada por Kohlbeck e Mayhew (2004; 2010) e Silveira, Prado e Sasso (2009). Como principais determinantes foram investigadas proxies para captar os efeitos dos mecanismos de governança corporativa e ambiente legal, do desempenho das empresas, dos desvios entre direitos sobre controle e direitos sobre fluxo de caixa e do excesso de remuneração executiva. Também foram adicionadas variáveis de controle para isolar as características intrínsecas das firmas. Nas análises econométricas foram estimados os modelos pelos métodos de Poisson, corte transversal agrupado (Pooled-OLS) e logit. A estimação foi feita pelo método dos mínimos quadrados ordinários (MQO), e para aumentar a robustez das estimativas econométricas, foram utilizadas variáveis instrumentais estimadas pelo método dos momentos generalizados (MMG). As evidências indicam que os fatores investigados impactam diferentemente as diversas medidas de TPRs das empresas analisadas. Verificou-se que os contratos relacionados, em geral, são danosos às empresas, impactando negativamente o desempenho delas, desempenho este que é aumentado pela presença de mecanismos eficazes de governança corporativa. Os resultados do impacto das medidas de governança corporativa e das características intrínsecas das firmas no desempenho das empresas são robustos à presença de endogeneidade com base nas regressões com variáveis instrumentais.

Efeitos do comitê de auditoria e do conselho fiscal na qualidade da informação contábil no Brasil

Esta dissertação foi desenvolvida com o objetivo de investigar os efeitos da instalação e das características do Conselho Fiscal e do Comitê de Auditoria sobre a qualidade das informações contábeis no Brasil. As características estudadas foram à independência e a qualificação dos membros. As proxies da qualidade da informação contábil foram relevância, tempestividade e conservadorismo condicional. A amostra utilizada foi composta por empresas brasileiras, listadas na Bolsa de Valores, Mercadorias e Futuros de São Paulo (BM&FBovespa), com liquidez anual superior a 0,001, no período de 2010 a 2013. Os dados foram coletados na base de dados Comdinheiro e nos Formulários de Referência das empresas, disponíveis no sítio eletrônico da Comissão de Valores Mobiliários (CVM) ou BM&FBovespa. Os modelos de qualidade da informação foram adaptados ao recorte metodológico e estimados pelo método dos mínimos quadrados ordinários (MQO), com erros-padrão robustos clusterizados por firma. Os resultados revelaram efeitos da instalação dos órgãos analisados sobre as proxies de qualidade da informação contábil. A instalação do Conselho Fiscal impactou positivamente a relevância do patrimônio líquido, enquanto a instalação do Comitê de Auditoria, a relevância do lucro. Esses resultados podem indicar diferenças no direcionamento da atenção desses órgãos: em proteger o patrimônio da entidade para os acionistas (Conselho Fiscal) ou em assegurar números mais confiáveis sobre o desempenho dos administradores (Comitê de Auditoria). Paralelamente, os resultados para a instalação do Conselho Fiscal de forma permanente inferiu força desse órgão como mecanismo de controle, ao invés da instalação somente a pedido dos acionistas. Já, a implementação do Conselho Fiscal Turbinado se mostrou ineficiente no controle da qualidade das informações contábeis. Na análise das características, a independência dos membros do Comitê de Auditoria impactou a relevância do lucro. Ao passo que a independência do Conselho Fiscal impactou a relevância do patrimônio líquido e o conservadorismo condicional (reconhecimento oportuno de perdas econômicas). Essas associações foram mais significantes quando os membros do Conselho Fiscal eram independentes dos acionistas controladores. Na análise da qualificação dos membros, foram encontradas evidências positivas na relação entre a relevância do patrimônio líquido e a maior proporção de membros do Conselho Fiscal com qualificação em Business (Contabilidade, Administração e Economia). O conservadorismo condicional foi maior na medida em que a qualificação dos membros do Conselho Fiscal convergia para a Contabilidade. Os resultados da qualificação dos membros do Comitê de Auditoria demonstraram relevância do lucro na presença de, ao menos, um Contador e na maior proporção de membros com qualificação tanto em Contabilidade como em Business; sendo mais significante conforme a qualificação dos membros do Comitê de Auditoria convergia para a Contabilidade.

Fatores determinantes da política de distribuição de dividendos: Evidência empírica para as empresas não financeiras da Euronext Lisbon

Dividends and their distribution decisions, being a component of the compensation of investors are a constant financial worry within companies, thus revealing one of the themes highlighted in the context of the financial literature. Study will address the factors determining the dividend policy practiced by companies listed in the Portuguese stock market. The latter will be 47 non-financial companies listed on the Euronext Lisbon during 2009 until 2011. The two samples that have been investigated include the representative of the majority of non-financial companies listed on Euronext Lisbon and the other financial companies members of the PSI 20. The methodology adopted is one of the ordinary least squares regression and the amount of dividends per share distributed was used in determining the dependent variable. In relation to the independent variables, six explanatory factors were chosen. These include profitability, stability of dividend policy, size, growth, risk and investment opportunities. The conclusion suggests that the most important factors to explain the amount of dividends distributed are profitability and stability of dividend policy. There after, growth and risk factors, as well as factors that explain the amount of dividends distributed are also relevant. The remaining variables obtained were insufficient evidence pointing to a significant effect in explaining the dividend policy of Portuguese companies in the sample. The conclusion also states that differences exist in the importance of the explanatory factors to the amount of dividends distributed between the study samples, given the differentiation of dividend policies, followed by companies from each group analyzed.

Desempenho empresarial e o valor da empresa no mercado de capitais: evidência empírica para o mercado de capitais português

The main objective of this paper is to analyse the effect of firms’ performance indicators in explaining the price of stocks in the Portuguese capital market, using a fundamental analysis. In the empirical setting, firms’ performance indicators are gathered into two groups: (1) economic and financial indicators and (2) stock market indicators. Using a sample of 38 firms quoted at Euronext Lisbon, estimates are obtained trough an Ordinary Least Squares (OLS) model and report to December, 31 2007. Results suggest that performance indicators are able to explain the firms’ stock market price. There is a significant positive impact of sales growth and of payout ratio, while we find a statistically significant negative effect of the firm’s financial autonomy on the stock market price for the majority of firms quoted at Euronext Lisbon.

Inovatividade, envolvimento, atitude e experiência na adoção da compra on-line

Este trabalho procura analisar as inter-relações entre a inovatividade, o envolvimento, a atitude dentro do modelo Theory of Planned Behavior (TPB) decomposto desenvolvido na psicologia social, e a experiência com a Internet com o processo de adoção da compra pela internet. Foi elaborado um modelo integrativo que possibilitasse explicar a relação entre esses fatores e a compra pela internet, e foi desenvolvida uma pesquisa de campo considerando uma amostra não probabilística de estudantes. Foi utilizado o método multivariado de modelagem de equações estruturais, aplicado por meio da técnica Partial Least Squares (PLS) para a verificação, explicação e comparação das relações entre os construtos. Os resultados mostram que a intenção da compra pela internet é diretamente influenciada pela atitude e pela inovatividade, e a atitude é influenciada pelo envolvimento. Não foi encontrada relação entre a experiência com a internet e a compra pela internet.

Simulation of default events in a CDX and estimation of the spread

The portfolio generating the iTraxx EUR index is modeled by coupled Markov chains. Each of the industries of the portfolio evolves according to its own Markov transition matrix. Using a variant of the method of moments, the model parameters are estimated from a data set of Standard and Poor's. Swap spreads are evaluated by Monte-Carlo simulations. Along with an actuarially fair spread, at least squares spread is considered.

Fungos endofíticos em Eugenia brasiliensis: prospecção química, biológica, enzimática e avaliação do co-cultivo e epigenética em Xylaria cubensis, Diaporthe sp. e Colletotrichum sp.

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Geographical, temporal and environmental determinants of bryophyte species richness in the Macaronesian Islands

Copyright: © 2014 Aranda et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Interlaboratory validation of an environmental monitoring method for trace analysis of endocrine disrupting compounds

Environmental pollution continues to be an emerging study field, as there are thousands of anthropogenic compounds mixed in the environment whose possible mechanisms of toxicity and physiological outcomes are of great concern. Developing methods to access and prioritize the screening of these compounds at trace levels in order to support regulatory efforts is, therefore, very important. A methodology based on solid phase extraction followed by derivatization and gas chromatography-mass spectrometry analysis was developed for the assessment of four endocrine disrupting compounds (EDCs) in water matrices: bisphenol A, estrone, 17b-estradiol and 17a-ethinylestradiol. The study was performed, simultaneously, by two different laboratories in order to evaluate the robustness of the method and to increase the quality control over its application in routine analysis. Validation was done according to the International Conference on Harmonisation recommendations and other international guidelines with specifications for the GC-MS methodology. Matrix-induced chromatographic response enhancement was avoided by using matrix-standard calibration solutions and heteroscedasticity has been overtaken by a weighted least squares linear regression model application. Consistent evaluation of key analytical parameters such as extraction efficiency, sensitivity, specificity, linearity, limits of detection and quantification, precision, accuracy and robustness was done in accordance with standards established for acceptance. Finally, the application of the optimized method in the assessment of the selected analytes in environmental samples suggested that it is an expedite methodology for routine analysis of EDC residues in water matrices.

Quantification of endocrine disruptors and pesticides in water by gas chromatography–tandem mass spectrometry. Method validation using weighted linear regression schemes

Amulti-residue methodology based on a solid phase extraction followed by gas chromatography–tandem mass spectrometry was developed for trace analysis of 32 compounds in water matrices, including estrogens and several pesticides from different chemical families, some of them with endocrine disrupting properties. Matrix standard calibration solutions were prepared by adding known amounts of the analytes to a residue-free sample to compensate matrix-induced chromatographic response enhancement observed for certain pesticides. Validation was done mainly according to the International Conference on Harmonisation recommendations, as well as some European and American validation guidelines with specifications for pesticides analysis and/or GC–MS methodology. As the assumption of homoscedasticity was not met for analytical data, weighted least squares linear regression procedure was applied as a simple and effective way to counteract the greater influence of the greater concentrations on the fitted regression line, improving accuracy at the lower end of the calibration curve. The method was considered validated for 31 compounds after consistent evaluation of the key analytical parameters: specificity, linearity, limit of detection and quantification, range, precision, accuracy, extraction efficiency, stability and robustness.

Brownian motion with drift threshold model

In this thesis we implement estimating procedures in order to estimate threshold parameters for the continuous time threshold models driven by stochastic di®erential equations. The ¯rst procedure is based on the EM (expectation-maximization) algorithm applied to the threshold model built from the Brownian motion with drift process. The second procedure mimics one of the fundamental ideas in the estimation of the thresholds in time series context, that is, conditional least squares estimation. We implement this procedure not only for the threshold model built from the Brownian motion with drift process but also for more generic models as the ones built from the geometric Brownian motion or the Ornstein-Uhlenbeck process. Both procedures are implemented for simu- lated data and the least squares estimation procedure is also implemented for real data of daily prices from a set of international funds. The ¯rst fund is the PF-European Sus- tainable Equities-R fund from the Pictet Funds company and the second is the Parvest Europe Dynamic Growth fund from the BNP Paribas company. The data for both funds are daily prices from the year 2004. The last fund to be considered is the Converging Europe Bond fund from the Schroder company and the data are daily prices from the year 2005.

Cross-cultural validity of the demand-control questionnaire: Swedish and Brazilian workers

OBJECTIVE To evaluate the cross-cultural validity of the Demand-Control Questionnaire, comparing the original Swedish questionnaire with the Brazilian version. METHODS We compared data from 362 Swedish and 399 Brazilian health workers. Confirmatory and exploratory factor analyses were performed to test structural validity, using the robust weighted least squares mean and variance-adjusted (WLSMV) estimator. Construct validity, using hypotheses testing, was evaluated through the inspection of the mean score distribution of the scale dimensions according to sociodemographic and social support at work variables. RESULTS The confirmatory and exploratory factor analyses supported the instrument in three dimensions (for Swedish and Brazilians): psychological demands, skill discretion and decision authority. The best-fit model was achieved by including an error correlation between work fast and work intensely (psychological demands) and removing the item repetitive work (skill discretion). Hypotheses testing showed that workers with university degree had higher scores on skill discretion and decision authority and those with high levels of Social Support at Work had lower scores on psychological demands and higher scores on decision authority. CONCLUSIONS The results supported the equivalent dimensional structures across the two culturally different work contexts. Skill discretion and decision authority formed two distinct dimensions and the item repetitive work should be removed.

Modelação estatística das co-infecções da SIDA em países da União Europeia

Dissertação apresentada para obtenção do Grau de Doutor em Matemática, especialidade de Estatística, pela Universidade Nova de Lisboa, Faculdade de Ciências e Tecnologia

PLSR Models for Mechanical Strengths of Concrete Composite Materials Reinforced with Pultrusion Wastes

In this paper, we present two Partial Least Squares Regression (PLSR) models for compressive and flexural strength responses of a concrete composite material reinforced with pultrusion wastes. The main objective is to characterize this cost-effective waste management solution for glass fiber reinforced polymer (GFRP) pultrusion wastes and end-of-life products that will lead, thereby, to a more sustainable composite materials industry. The experiments took into account formulations with the incorporation of three different weight contents of GFRP waste materials into polyester based mortars, as sand aggregate and filler replacements, two waste particle size grades and the incorporation of silane adhesion promoter into the polyester resin matrix in order to improve binder aggregates interfaces. The regression models were achieved for these data and two latent variables were identified as suitable, with a 95% confidence level. This technological option, for improving the quality of GFRP filled polymer mortars, is viable thus opening a door to selective recycling of GFRP waste and its use in the production of concrete-polymer based products. However, further and complementary studies will be necessary to confirm the technical and economic viability of the process.