Likelihood-based inference for the transmuted log-logistic model in the presence of right-censored data

Although new transmuted distributions have been widely proposed in the last few years, it is rarely to find those class of models applied in survival analysis in the presence of censored lifetimes. In this context, we are concerned in applying the transmuted log-logistic model in the study of discharge times of patients treated with the Linezolid drug. For model fitting, we use and compare different profile likelihood methods. Analysis of residuals and influence are also presented. All results are validated in a simulation study by considering the bootstrap techniques.     

EASING THE CONSTRAINTS OF MOTHERHOOD: THE EFFECTS OF ALL‐DAY SCHOOLS ON MOTHERS' LABOR SUPPLY

Low rates of female labor force participation (LFP) have been linked to the absence of childcare policies. This article examines the degree to which extending the school day by 3.5 hours in elementary schools, a large implicit childcare subsidy, affects LFP, the number of weekly hours worked, and the monthly earnings of females with elementary‐school‐age children. To do so, we exploit within‐individual variation in access to full‐time schools and a rotating panel of households that contains 12 years of individual‐level data on labor outcomes and sociodemographic characteristics. Results from long‐difference models show that extending the school day increases mothers' labor supply, increasing LFP by 5.5 percentage points and the number of weekly hours worked by 1.8. Moreover, these increases are accompanied by a raise in monthly earnings. (JEL I25, J13, J22)     

Women and poverty: A gender-sensitive approach

Poverty is not a gender neutral condition as the number of poor women exceeds that concerning men and women and men experience poverty in distinctive ways. This paper discusses the relevance of incorporating a gender perspective in poverty studies and provides a portrait of poverty among women in Portugal. Following a multidimensional concept of poverty, the methodology used comprises a cross-sectional and a dynamic analysis of poverty, using data from ECHP (1995–2001). The results point to the importance of various factors contributing to women's vulnerability to poverty, such as issues related to labor market, lone motherhood, ageing and education.     

Solving Steiner Tree Problems in Graphs with Lagrangian Relaxation

This paper presents an algorithm to obtain near optimal solutions for the Steiner tree problem in graphs. It is based on a Lagrangian relaxation of a multi-commodity flow formulation of the problem. An extension of the subgradient algorithm, the volume algorithm, has been used to obtain lower bounds and to estimate primal solutions. It was possible to solve several difficult instances from the literature to proven optimality without branching. Computational results are reported for problems drawn from the SteinLib library.     

Operations research from the viewpoint of general systems theory

This paper examines the operations research process from the viewpoint of General Systems Theory. The components of the OR process and the relations between them are critically examined. The five components are: (1) the “reality” of the problem situation, (2) the conceptual model of the problem situation, (3) the scientific model of the conceptual model, (4) the solution to the scientific model, and (5) the implementation of the solution. The paper argues that we have sub-optimized both our knowledge (study) and our application of the OR process. That is, there have been extremely few studies and applications of OR which have concerned themselves with OR from a whole systems point of view. The paper argues that without a whole systems perspective OR can neither be understood nor effectively applied.     

Ethnic pride, biculturalism, and drug use norms of urban American Indian adolescents

This study examines how strength of ethnic identity, multiethnic identity, and other indicators of biculturalism relate to the drug use norms of urban American Indian middle school students. The article distinguishes categories of norms that may affect drug use. Regression analysis of self-reports by 434 American Indian seventh graders attending middle schools in a large southwestern U.S. city indicated that students who had a more intense sense of ethnic pride adhered more strongly to certain antidrug norms than those who did not. Whereas American Indian students with better grades in school held consistently stronger antidrug norms, there were few differences by gender, socioeconomic status, or age. These results have implications in social work practice for better understanding and strengthening the protective aspects of American Indian culture in drug prevention efforts.     

The Poisson–exponential distribution: a Bayesian approach

In this paper, we proposed a new two-parameter lifetime distribution with increasing failure rate. The new distribution arises on a latent complementary risk scenario. The properties of the proposed distribution are discussed, including a formal proof of its density function and an explicit algebraic formulae for its quantiles and survival and hazard functions. Also, we have discussed inference aspects of the model proposed via Bayesian inference by using Markov chain Monte Carlo simulation. A simulation study investigates the frequentist properties of the proposed estimators obtained under the assumptions of non-informative priors. Further, some discussions on models selection criteria are given. The developed methodology is illustrated on a real data set.