Efficiency of a Linear Combination of the Median and the Sample Mean: The Double Truncated Normal Distribution

Abstract.  We characterize all symmetric location models for which a linear combination of the median and the sample mean is an asymptotically efficient estimator of the location parameter. The resulting model can be understood as a symmetrized or double truncated normal distribution. A simple algorithm to estimate the parameters is given and an application is presented.     

Implementation and evaluation of an HIV/STD intervention in Peru

This paper presents the lessons learned through a process evaluation (PE) after 1 year of implementation of a 2-year community intervention in Lima, Peru. The intervention consisted of training and motivating community popular opinion leaders (CPOLs) for three marginal population segments to disseminate prevention messages among their peers. PE data included: observations, qualitative interviews with CPOLS, conversations and messages delivered by CPOLs, training facilitators' perceptions about implementation, and a survey of CPOLs. The PE helped to document and enhance the intervention. CPOLs were motivated to talk to their peers. CPOLs perceived that their participation had an effect on their own risk behaviors and saw their role as beneficial to their community. The PE was helpful in examining training delivery and the feasibility and acceptability of the intervention in order to assess the elements related to program success necessary to replicate the CPOL model.     

Perceptions of power and the management of environmental conflict: Forest politics in British Columbia

Political actors' perceptions of the contexts in which they act influence their strategies and behavior. A key element of political contexts is the configuration of power with respect to a conflict. We interviewed 28 individuals involved in British Columbia forest politics to determine their perceptions of the configuration of power, the nature of their political behavior, their dispositions with respect to institutionalized conflict resolution processes, and their policy goals. Our analysis generated two sets of conclusions. First, the B.C. government's efforts to address forest conflict will be hindered by the inconsistency between the conflict management strategy they have chosen and the mental models of politics held by key political actors. Second, the subjective realities of political actors can be used to explain variation in political behavior.     

Empirical likelihood for nonlinear models with missing responses

In this paper, a nonlinear model with response variables missing at random is studied. In order to improve the coverage accuracy for model parameters, the empirical likelihood (EL) ratio method is considered. On the complete data, the EL statistic for the parameters and its approximation have a χ² asymptotic distribution. When the responses are reconstituted using a semi-parametric method, the empirical log-likelihood on the response variables associated with the imputed data is also asymptotically χ². The Wilks theorem for EL on the parameters, based on reconstituted data, is also satisfied. These results can be used to construct the confidence region for the model parameters and the response variables. It is shown via Monte Carlo simulations that the EL methods outperform the normal approximation-based method in terms of coverage probability for the unknown parameter, including on the reconstituted data. The advantages of the proposed method are exemplified on real data.     

Maximum likelihood estimator in a multi-phase random regression model

We consider a random regression model with several-fold change-points. The results for one change-point are generalized. The maximum likelihood estimator of the parameters is shown to be consistent, and the asymptotic distribution for the estimators of the coefficients is shown to be Gaussian. The estimators of the change-points converge, with n ^?1 rate, to the vector whose components are the left end points of the maximizing interval with respect to each change-point. The likelihood process is asymptotically equivalent to the sum of independent compound Poisson processes.     

Counterdiagonal/nonpositive tail dependence in Vine copula constructions: application to portfolio management

Statistical Methods & Applications - Accurately modelling the dependence structure between financial assets in a portfolio optimization framework has attracted growing attention in statistical...     

Latent Tuberculosis Infection Screening Acceptability among Migrant Farmworkers

Latent tuberculosis (TB) infection is routinely diagnosed using the tuberculin skin test (TST). New methods of detection more specific than TST such as QuantiFERON TB Gold In‐Tube (QFT‐GIT) have been developed but evidence remains limited on their acceptability among migrant farmworkers. This article examined the acceptability of screening tests among migrant farmworkers working on the Arizona‐Mexico border. We conducted a cross‐sectional survey of migrant farmworkers via questionnaire. Of 83 participants interviewed, 53 (63.9%) believed that TB was a serious disease that could result in death and 59 (71.1%) considered TB a health concern in their community. Sixty‐four participants (77.1%) rated QFT‐GIT test as performing better than TST. Our study demonstrates preference for QFT‐GIT results over TST, and highlights migrant farmworkers’ considering themselves at risk of TB and TB as a health concern. Policies that create easy access and culturally appropriate, affordable healthcare for this vulnerable population should be encouraged.     

Incorporation of Migrant Students Returning From the United States to High Schools in Mexico

The purpose of this research was to identify the difficulties faced by the Mexican migrant students when incorporated into the Mexican education system after having studied in the United States of America. Thirty migrant middle school students, two principals, two social workers and one teacher participated in the study. The study (conducted in two phases) collected information regarding: school admission, adjustment to the school organization, adaptation to learning situations and the perception of school belonging. The main problems found during the admission and enrolment procedures in Mexican schools are: language use, diagnostic assessment, didactic processes that take place in the classroom, complementary support activities, grade repetition, very little family involvement and the separation of the students from their migrant parents.     

Does Living in a Fatherless Household Compromise Educational Success? A Comparative Study of Cognitive and Non-cognitive Skills

This study addresses the relationship between various family forms and the level of cognitive and non-cognitive skills among 15- to 16-year-old students. We measure cognitive skills using standardized scores in mathematics; non-cognitive abilities are captured by a composite measure of internal locus of control related to mathematics. A particular focus lies on father absence although we also examine the role played by co-residence with siblings and grandparents. We use cross-nationally comparable data on students participating in the Programme for International Student Assessment’s release for 2012. By mapping inequalities by family forms across 33 developed countries, this study provides robust cross-country comparable evidence on the relationship of household structure with both cognitive and non-cognitive skills. The study produces three key results: first, the absence of fathers from the household as well as co-residence with grandparents is associated with adverse outcomes for children in virtually all developed countries. Second, this is generally true in terms of both cognitive and non-cognitive skills, although the disadvantage connected to both family forms is notably stronger in the former than in the latter domain. Finally, there is marked cross-national diversity in the effects associated with the presence in the household of siblings and especially grandparents which furthermore differs across the two outcomes considered.