Asymptotic distribution of least square estimators for linear models with dependent errors

In this paper, we consider the usual linear regression model in the case where the error process is assumed strictly stationary. We use a result from Hannan (Central limit theorems for time series regression. Probab Theory Relat Fields. 1973;26(2):157–170), who proved a Central Limit Theorem for the usual least squares estimator under general conditions on the design and on the error process. Whatever the design satisfying Hannan's conditions, we define an estimator of the covariance matrix and we prove its consistency under very mild conditions. As an application, we show how to modify the usual tests on the linear model in this dependent context, in such a way that the type-I error rate remains asymptotically correct, and we illustrate the performance of this procedure through different sets of simulations.     

Inequality in Education and Wealth in Tanzania: A 25-Year Perspective

Social Indicators Research - The literature on inequality in Tanzania has been dependent on limited rounds of methodologically different household budget surveys. The literature in question...     

An Overview of a Multimedia Benchmarking Analysis for Three Risk Assessment Models: RESRAD, MMSOILS, and MEPAS

Multimedia modelers from the United States Environmental Protection Agency (EPA) and the United States Department of Energy (DOE) collaborated to conduct a detailed and quantitative benchmarking analysis of three multimedia models. The three models—RESRAD (DOE), MMSOILS (EPA), and MEPAS (DOE)—represent analytically-based tools that are used by the respective agencies for performing human exposure and health risk assessments. The study is performed by individuals who participate directly in the ongoing design, development, and application of the models. Model form and function are compared by applying the models to a series of hypothetical problems, first isolating individual modules (e.g., atmospheric, surface water, groundwater) and then simulating multimedia-based risk resulting from contaminant release from a single source to multiple environmental media. Study results show that the models differ with respect to environmental processes included (i.e., model features) and the mathematical formulation and assumptions related to the implementation of solutions. Depending on the application, numerical estimates resulting from the models may vary over several orders-of-magnitude. On the other hand, two or more differences may offset each other such that model predictions are virtually equal. The conclusion from these results is that multimedia models are complex due to the integration of the many components of a risk assessment and this complexity must be fully appreciated during each step of the modeling process (i.e., model selection, problem conceptualization, model application, and interpretation of results).     

Testing Infants' Discrimination With the Orientation Latency Procedure

A new discrimination procedure based on the measurement of visual orientation latency to speech stimuli is introduced. Each participant listens to a series of short familiarization test trials. In each trial, 5 to 7 centrally‐presented familiarization stimuli are followed by laterally‐presented test stimuli. Infants were found to orient faster to different‐category than to same‐category test stimuli. This result was found despite a high degree of prosodic variability in the familiarization and test stimuli introduced by changes in talker and speaking rate. The combination of a multitrial design with use of acoustic and prosodic variability seems suitable for studying the representation of phonological categories.     

The investment of social security reserves during periods of crisis: The experience of Cameroon

The crisis which Cameroon has been going through since 1986 has affected the various sectors of its economic and social life. For the first time since its establishment, the social security system administered by the National Social Insurance Fund is experiencing serious difficulties. After a period of financial surplus during which it accumulated substantial reserves, the product of the Fund's contributions has not covered its expenditure since the 1988/89 financial year, thereby obliging it to draw upon its reserves to balance its budget. After examining the fundamental criteria which have to be followed in the investment of social security assets, in accordance with the objectives and principles governing the financing of the system, the author of this article looks at the various types of investment undertaken by the Fund during its period of prosperity. "he resulting assessment leads to a series of recommendations for the formulation of a sound investment policy and the rational management of social security investment portfolios".     

Sequential design of computer experiments for the estimation of a probability of failure

This paper deals with the problem of estimating the volume of the excursion set of a function f:ℝ ^d →ℝ above a given threshold, under a probability measure on ℝ ^d that is assumed to be known. In the industrial world, this corresponds to the problem of estimating a probability of failure of a system. When only an expensive-to-simulate model of the system is available, the budget for simulations is usually severely limited and therefore classical Monte Carlo methods ought to be avoided. One of the main contributions of this article is to derive SUR (stepwise uncertainty reduction) strategies from a Bayesian formulation of the problem of estimating a probability of failure. These sequential strategies use a Gaussian process model of f and aim at performing evaluations of f as efficiently as possible to infer the value of the probability of failure. We compare these strategies to other strategies also based on a Gaussian process model for estimating a probability of failure.     

Multivariate Pareto Distributions: Inference and Financial Applications

Univariate Pareto distributions are extensively studied. In this article, we propose a Bayesian inference methodology in the context of multivariate Pareto distributions of the second kind (Mardia's type). Computational techniques organized around Gibbs sampling with data augmentation are proposed to implement Bayesian inference in practice. The new methods are shown to work well in artificial examples involving a trivariate distribution, and to an empirical application involving daily exchange rate data for four major currencies.     

The impacts of climate variability on household welfare in rural Mexico

In light of the expected increase in weather variability from climate change, we examine the impact of weather shocks, defined as rainfall or growing degree days more than a standard deviation from their respective long-run means, on household consumption per capita. The analyses suggest that both rainfall and temperature shocks affect both food and non-food consumption. Furthermore, the results show that a household’s ability to protect its consumption from weather shocks depends on the climate region and when in the agricultural year the shock occurs. Especially, households in arid climates are not fully protected from weather shocks occurring during the beginning of the wet season (April, May, June). The results highlight the necessity to account for the underlying climatic variation as well as to carefully define the shocks.     

Anal Cancer Screening: Barriers and Facilitators Among Ethnically Diverse Gay, Bisexual, Transgender, and Other Men Who Have Sex With Men

Knowledge and beliefs about anal cancer screening among gay and other men who have sex with men remains unclear, despite data that suggests significant risk for intra-anal HPV-related cancers. Nevertheless, community-based screening activities may be most effective when stake-holder perspectives are addressed. We conducted four focus groups among 16 male and 3 female health care advocates experienced in working with diverse gay and other men who have sex with men in Los Angeles. Barriers to anal cancer screening included lack of awareness, stigma, psychological and physical discomfort, the anus as hidden/private, primary concern with HIV, and men's lack of healthcare seeking. Facilitators were community screening sites, novel strategies such as home testing, health care system changes and targeted educational campaigns, which may increase anal cancer awareness and screening among ethnically diverse men who have sex with men.     

Ownership and Control in Closely‐held Family‐owned Firms: An Exploration of Strategic and Operational Control

Much of the existing research into the divorce of ownership and control either focuses on the propensity for the separation of decision functions or upon scrutinizing conceptions, gauges or the practicalities of organizational control in large corporations. Although far from equivocal, such research appears broadly to concur that where ownership is dispersed, de facto control is likely to be exerted by management and that where ownership is closely‐held, de facto as well as legal control is exerted by owners. This study examines this assumption through exploring the nature of control in a closely‐held family firm. In this regard, the focus of this study is not on consequences of divorced ownership and control but rather on exploring the contingencies where ownership and control diverge. This research reveals a case wherein a closely‐held family firm is strategically and operationally controlled by its managers. Case research leads to the development of a range of insights regarding the owner/family and the management characteristics that contribute to this scenario. The paper concludes with a series of implications and conclusions.