Análise comparativa e teste empírico da validade dos modelos CAPM tradicional e condicional: o caso das ações da Petrobrás

ALVES, Janaína da Silva. Análise comparativa e teste empírico da validade dos modelos CAPM tradicional e condicional: o caso das ações da Petrobrás. Revista Ciências Administrativas, Fotaleza, v. 13, n. 1, p.147-157, ago. 2007.

Lógica condicional

The main goal of this work is to clarify the central concepts involved in the study of formalization of conditional sentences. More specifically, it has been done a comparative analysis of the two greater and more traditional proposals of conditional formalization (Lewis 1973c e Adams 1975). These proposals were responsible for the creation of a way of analysis that still present in the current debate about this subject. This work pursues to explain the principal assumptions held within these proposals. According to certain disambiguation techniques from Bennett (2003) and Lycan (2005), this work tries to explicit how these assumptions connect to the aims sought by the initial approaches. The following results show that there is a not declared presumption, the definition of the object of study of these theories, i.e., the definition of conditional sentence. This work argues that despite of not explicitly declared the definition of the study object has a central role in the intelligibility of the debate itself

Análise comparativa e teste empírico da validade dos modelos CAPM tradicional e condicional: o caso das ações da Petrobrás

ALVES, Janaína da Silva. Análise comparativa e teste empírico da validade dos modelos CAPM tradicional e condicional: o caso das ações da Petrobrás. Revista Ciências Administrativas, Fotaleza, v. 13, n. 1, p.147-157, ago. 2007.

Avaliação dos impactos do programa bolsa família na renda, na educação e no mercado de trabalho das famílias pobres do Brasil

This study aims to verify the impact of the Bolsa Família Program (BFP) in income and school attendance of poor Brazilian families. It is intended to also check the existence of a possible negative effect of the program on the labor market, titled as sloth effect. For such, microdata from the IBGE Census sample in 2010 were used. Seeking to purge possible selection biases, methodology of Quantilic Treatment Effect (QTE) was applied, in particular the estimator proposed by Firpo (2007), which assumes an exogenous and non-conditional treatment. Moreover, Foster- Greer-Thorbecke (FGT) index was calculated to check if there are fewer households below the poverty line, as well as if the inequality among the poor decreases. Human Opportunity Index (HOI) was also calculated to measure the access of young people / children education. Results showed that BFP has positively influenced the family per capita income and education (number of children aged 5-17 years old attending school). As for the labor market (worked hours and labor income), the program showed a negative effect. Thus, when compared with not benefiting families, those families who receive the BFP have: a) a higher family income (due to the shock of the transfer budget money) b) more children attending school (due to the conditionality imposed by the program); c) less worked hours (due to sloth effect in certain family groups) and d) a lower income from work. All these effects were potentiated separating the sample in the five Brazilian regions, being observed that the BFP strongly influenced the Northeast, showing a greater decrease in income inequality and poverty, and at the same time, achieved a greater negative impact on the labor market

Lógica por trás dos contratos sociais

Natural selection shapes body and behavior of each species. For primates, the social environment constituted one of the greatest selective pressure for the development of their cognition. When we consider gender differences, we see that sexual selection also operates through different selective pressures for men and women not only in physical terms but in terms of cognitive skills. Among these, the primary cognitive abilities - that emerge naturally - and secondary - that rely on an artificial environment for learning - develop differently for each sex, making them suitable for specific tasks in different capacities. Previous studies utilized the Wason Selection Test a conditional logic tool - to measure, among several other things, the ability to recognize violation of rules in abstract contexts and social contexts. Subjects generally had better performance in the latter, however, in these studies possible differences motivated by learning in formal logic or genre were not considered. Our study investigated these two variables, as well as the time spent to solve each task. Furthermore, we used an index to take into account the rights and wrongs of the participants in tasks. We realized that although learning in formal logic does not bring significant differences in solving tests, the gender differences are strongly observed when we consider the social contexts and abstract. Women perform better in social tasks. This can be explained due to different sexual selective pressures for this gender in terms of one-on-one relationships within the group. Men are better at tasks of abstract context and this is probably due to the same reason. Their capabilities for territory defense, habitat navigation and forming coalitions depends on primary cognitive abilities that support secondary cognitive skills of abstraction. Thus, gender differences are a factor to be taken into account in controlling future experiments with the same tool

Estimação e previsão no processo INARCH(2)

In the last decades the study of integer-valued time series has gained notoriety due to its broad applicability (modeling the number of car accidents in a given highway, or the number of people infected by a virus are two examples). One of the main interests of this area of study is to make forecasts, and for this reason it is very important to propose methods to make such forecasts, which consist of nonnegative integer values, due to the discrete nature of the data. In this work, we focus on the study and proposal of forecasts one, two and h steps ahead for integer-valued second-order autoregressive conditional heteroskedasticity processes [INARCH (2)], and in determining some theoretical properties of this model, such as the ordinary moments of its marginal distribution and the asymptotic distribution of its conditional least squares estimators. In addition, we study, via Monte Carlo simulation, the behavior of the estimators for the parameters of INARCH(2) processes obtained using three di erent methods (Yule- Walker, conditional least squares, and conditional maximum likelihood), in terms of mean squared error, mean absolute error and bias. We present some forecast proposals for INARCH(2) processes, which are compared again via Monte Carlo simulation. As an application of this proposed theory, we model a dataset related to the number of live male births of mothers living at Riachuelo city, in the state of Rio Grande do Norte, Brazil.

Estimação e previsão no processo INARCH(2)

In the last decades the study of integer-valued time series has gained notoriety due to its broad applicability (modeling the number of car accidents in a given highway, or the number of people infected by a virus are two examples). One of the main interests of this area of study is to make forecasts, and for this reason it is very important to propose methods to make such forecasts, which consist of nonnegative integer values, due to the discrete nature of the data. In this work, we focus on the study and proposal of forecasts one, two and h steps ahead for integer-valued second-order autoregressive conditional heteroskedasticity processes [INARCH (2)], and in determining some theoretical properties of this model, such as the ordinary moments of its marginal distribution and the asymptotic distribution of its conditional least squares estimators. In addition, we study, via Monte Carlo simulation, the behavior of the estimators for the parameters of INARCH(2) processes obtained using three di erent methods (Yule- Walker, conditional least squares, and conditional maximum likelihood), in terms of mean squared error, mean absolute error and bias. We present some forecast proposals for INARCH(2) processes, which are compared again via Monte Carlo simulation. As an application of this proposed theory, we model a dataset related to the number of live male births of mothers living at Riachuelo city, in the state of Rio Grande do Norte, Brazil.

Associação da depressão e distúrbio do sono em pacientes com e sem disfunção temporomandibular

Objective: To evaluate the inter-relationship between TMD (temporomandibular disorder), depression and sleep disorder. Methods: This is a case-control study with questionnaires in 111 patients, allocated from the Dentistry Department of UFRN, Natal, Brazil, from September 2014 to June 2015, for evaluation of depressive symptoms through the BDI (Beck Depression Inventory); sleep disorder, the PSQI (Pittsburgh Sleep Quality Index) and DTM through the RDC / TMD (diagnostic criteria to search for DTM). All indexes were applied by a single examiner previously trained and calibrated. The collected data were analyzed with chi-square tests of Pearson (χ2) and the unconditional logistic regression. Results: women had a risk of 2.85 times more likely to develop TMD (p = 0.046). The OR (odds ratio) shows that sleep disturbance increases by 2.19 the chances of having TMD (p = 0.062) and depressive symptoms increase the risk by 3.16 times in developing dysfunction (p = 0.053). Conclusion: The data of this research allows us to conclude that patients with TMD, in this population, were more likely to develop changes in sleep and depressive symptoms.