Robust estimation methods for exponential data: a monte-carlo comparison

We compare the performance of seven robust estimators for the parameter of an exponential distribution. These include the debiased median and two optimally-weighted one-sided trimmed means. We also introduce four new estimators: the Transform, Bayes, Scaled and Bicube estimators. We make the Monte Carlo comparisons for three sample sizes and six situations. We evaluate the comparisons in terms of a new performance measure, Mean Absolute Differential Error (MADE), and a premium/protection interpretation of MADE. We organize the comparisons to enhance statistical power by making maximal use of common random deviates. The Transform estimator provides the best performance as judged by MADE. The singly-trimmed mean and Transform method define the efficient frontier of premium/protection.     

Orthogonally Blocked Mixture Experiments in Ellipsoidal Restricted Regions

In practical situations involving mixtures formed from several ingredients, interest is sometimes centered on the response in an ellipsoidal neighborhood around a standard formulation. We show that standard, orthogonally blocked, response surface designs, defined on a q ? 1 dimensional unit sphere, may be transformed into similarly orthogonally blocked q-ingredient mixture designs defined within an ellipsoid centered at the standard formulation. The method is illustrated using several examples of mixture experiments with three, four, and five ingredients, arranged in two, three, or four orthogonal blocks, obtained by projecting standard central composite designs and Box–Behnken designs into the ellipsoidal mixture region. Rotations of the resulting designs within the ellipsoidal regions are also considered.     

Practical bayesian approaches to the analystcs of a 2×2 contingency table with incompletely categorized data

To assess the efficacy of a treatment, patients are administered a pre-test, the treatment, and a post-test (identical to the pre-test). These patients are then categorized according to their outcomes observed on both tests,e.g., (S,S), (S,F), etc. Also, we observe "incomplete" information on the pre-tests' outcomes for some patients and the results of only the post-test being known for thers, A Bayesian framework is fit to the problem and Bayes factors, posterior odds ratios, and utility functions are given to evaluate th e treatment, A method of assessing the prior distribution is specified and a numerical example is worked.     

On trends and constants in periodic autoregressions

Periodic autoregressions are characterised by autoregressive structures that vary with the season. If a time series is periodically integrated, one needs a seasonally varying differencing filter to remove the stochastic trend. When the periodic regression model contains constants and trends with unrestricted parameters, the data can show diverging seasonal deterministic trends. In this paper we derive explicit expressions for parameter restrictions that result in common deterministic trends under periodic trend stationarity and periodic integration.     

A Tiered Framework for Risk‐Relevant Characterization and Ranking of Chemical Exposures: Applications to the National Children's Study (NCS)

A challenge for large‐scale environmental health investigations such as the National Children's Study (NCS), is characterizing exposures to multiple, co‐occurring chemical agents with varying spatiotemporal concentrations and consequences modulated by biochemical, physiological, behavioral, socioeconomic, and environmental factors. Such investigations can benefit from systematic retrieval, analysis, and integration of diverse extant information on both contaminant patterns and exposure‐relevant factors. This requires development, evaluation, and deployment of informatics methods that support flexible access and analysis of multiattribute data across multiple spatiotemporal scales. A new “Tiered Exposure Ranking” (TiER) framework, developed to support various aspects of risk‐relevant exposure characterization, is described here, with examples demonstrating its application to the NCS. TiER utilizes advances in informatics computational methods, extant database content and availability, and integrative environmental/exposure/biological modeling to support both “discovery‐driven” and “hypothesis‐driven” analyses. “Tier 1” applications focus on “exposomic” pattern recognition for extracting information from multidimensional data sets, whereas second and higher tier applications utilize mechanistic models to develop risk‐relevant exposure metrics for populations and individuals. In this article, “tier 1” applications of TiER explore identification of potentially causative associations among risk factors, for prioritizing further studies, by considering publicly available demographic/socioeconomic, behavioral, and environmental data in relation to two health endpoints (preterm birth and low birth weight). A “tier 2” application develops estimates of pollutant mixture inhalation exposure indices for NCS counties, formulated to support risk characterization for these endpoints. Applications of TiER demonstrate the feasibility of developing risk‐relevant exposure characterizations for pollutants using extant environmental and demographic/socioeconomic data.     

Social Networks Derived from Affiliations and Friendships, Multi-informant and Self-reports: Stability, Concordance, Placement of Aggressive and Unpopular Children, and Centrality

This study compares three variations in how researchers construct middle childhood social networks: (1) with friendships or affiliations as a relational tie; (2) with children providing self reports of relationships, or in addition, multi-informant reports of relationships in which they are not involved; and (3) whether network computation is correlational or distance-based . The sample was 357 fourth- and fifth-grade students in 17 classrooms. The strongest differences were between self-reported friendship and affiliative networks. Results showed that compared with affiliations, friendship networks had smaller groups, more isolates, and lower fall-to-spring stability. Agreement in social placement between friendship and affiliative networks was generally average, but poor for unpopular and aggressive children. Multi-informant affiliative networks were most robust in their positioning of aggressive children. Multi-informant centrality was uniquely uncorrelated with aggression. Network computation differences were not substantial. Discussion focuses on recommendations for research and the educational promise of network technology.     

Gambling and Alcohol Use: Trends in the State of New Mexico from 1996–1998

Alcohol consumption and its relationship to gambling was examined in a statewide New Mexico survey in 1996 and 1998. Data regarding both drinking habits and gambling behavior were obtained from a stratified random sample of the adult population (N = 2674) across the entire State of New Mexico via phone survey. These surveys were carried out shortly after a period when New Mexico experienced an initial surge in the legalized gaming industry. Fifty-seven percent of survey respondents reported drinking in the past month, while 43.1% reported no drinking in the past 30 days. Results show that while the number of days in the past 30 that a person drinks is significantly correlated with some types of gambling behavior (e.g., in 1998, drinking more days was associated with more card gambling and sports gambling), it is the amount of alcohol consumed per occasion that is associated with more gambling behavior. For example, in both 1996 and 1998, drinking more per occasion was associated with more sports betting, dice gambling, number/lottery gambling, gambling using machines, and paper game gambling (e.g., pull tabs, punchboard). These results suggest that problem gambling behavior is not affected as much by the number of occasions on which one consumes alcohol, as by the amount of alcohol consumed per occasion.     

Auditors' Assessment of Management's Disposition: An Attributional Analysis*

Auditors' assessment of management's dispositions presumably affects their subsequent judgments. However, little is known about the process by which auditors infer characteristics of management. This paper proposes the theory of correspondent inferences [25] as a framework for examining auditors' assessment of management's dispositions; the model is tested in a laboratory experiment using experienced audit managers. The results are consistent with the proposed theoretical framework. Implications for future research are discussed.     

Labour Market Realism and the Global Compacts on Migration and Refugees

The Global Compacts on Migration (GCM) and Refugees (GCR) include policy recommendations that aim to increase opportunities for legal labour migration, improve protections for migrant workers, and provide refugees with ‘complementary pathways’ to enhanced protection via labour mobility. This paper explains why there are large gaps between these policy recommendations and the labour market policies and realities in the countries that host most of the world’s migrant workers. These gaps between ideals and realities are likely to limit the effective implementation of the GCM/GCR recommendations on labour migration. More ‘labour market realism‘ is needed to incrementally but effectively improve protections for migrant workers.     

Slavery, ‘respectability,’ and being ‘freeborn’ on the shores of nineteenth-century Lake Tanganyika

Concepts of slavery and freedom dominate the historiography of labour and social relations in nineteenth-century East and Central Africa. This article argues that such concepts oversimplify the complexity of other forms of servitude. It does so by analysing the position of people who referred to themselves as ngwana on the shores of Lake Tanganyika. Ngwana translates from Swahili as ‘gentlemen,’ and it implies ‘respectability’ and ‘freeborn’ status. Yet most ngwana could not claim to be free, even if they had ceased being slaves. Rather than freedom, ngwana sought ‘respect,’ and in so doing blurred the lines between slavery and freedom.