Gibbs sampling for marginal posterior expectations

In earlier work (Gelfand and Smith, 1990 and Gelfand et al, 1990) a sampling based approach using the Gibbs sampler was offered as a means for developing marginal posterior densities for a wide range of Bayesian problems several of which were previously inaccessible. Our purpose here is two-fold. First we flesh out the implementation of this approach for calculation of arbitrary expectations of interest. Secondly we offer comparison with perhaps the most prominent approach for calculating posterior expectations, analytic approximation involving application of the LaPlace method. Several illustrative examples are discussed as well. Clear advantages for the sampling based approach emerge.     

A New Malaysian Quality of Life Index Based on Fuzzy Sets and Hierarchical Needs

The Malaysian Quality of Life Index (MQLI) released by the Economic Planning Unit (EPU), has led authors to search for alternative method of expressing this index. One of the limitations in MQLI computations is the failure to recognise unequal weights for each accounted component. This paper offers a new way of expressing the quality of life index using a mathematical modelling based on fuzzy sets theory and the proposed weights based on Maslow’s theory of hierarchical human needs. The indices of 11 components that were used to compute MQLI, again be gathered as a basis in expressing a new Malaysian Fuzzy Quality of Life Index (MFQLI). The new indices for each component yielded through a normalisation process prior weighting and aggregation to compose a new MFQLI. It was found that a fuzzy sets approach with the inclusion of weights based on human needs yielded a better index of quality of life than the MQLI.     

Analyzing the Homeland Security of the U.S.-Mexico Border

We develop a mathematical optimization model at the intersection of homeland security and immigration, that chooses various immigration enforcement decision variables to minimize the probability that a terrorist can successfully enter the United States across the U.S.-Mexico border. Included are a discrete choice model for the probability that a potential alien crosser will attempt to cross the U.S.-Mexico border in terms of the likelihood of success and the U.S. wage for illegal workers, a spatial model that calculates the apprehension probability as a function of the number of crossers, the number of border patrol agents, and the amount of surveillance technology on the border, a queueing model that determines the probability that an apprehended alien will be detained and removed as a function of the number of detention beds, and an equilibrium model for the illegal wage that balances the supply and demand for work and incorporates the impact of worksite enforcement. Our main result is that detention beds are the current system bottleneck (even after the large reduction in detention residence times recently achieved by expedited removal), and increases in border patrol staffing or surveillance technology would not provide any improvements without a large increase in detention capacity. Our model also predicts that surveillance technology is more cost effective than border patrol agents, which in turn are more cost effective than worksite inspectors, but these results are not robust due to the difficulty of predicting human behavior from existing data. Overall, the probability that a terrorist can successfully enter the United States is very high, and it would be extremely costly and difficult to significantly reduce it. We also investigate the alternative objective function of minimizing the flow of illegal aliens across the U.S.-Mexico border, and obtain qualitatively similar results.     

An Empirical Approach to Sufficient Similarity: Combining Exposure Data and Mixtures Toxicology Data

When assessing risks posed by environmental chemical mixtures, whole mixture approaches are preferred to component approaches. When toxicological data on whole mixtures as they occur in the environment are not available, Environmental Protection Agency guidance states that toxicity data from a mixture considered “sufficiently similar” to the environmental mixture can serve as a surrogate. We propose a novel method to examine whether mixtures are sufficiently similar, when exposure data and mixture toxicity study data from at least one representative mixture are available. We define sufficient similarity using equivalence testing methodology comparing the distance between benchmark dose estimates for mixtures in both data‐rich and data‐poor cases. We construct a “similar mixtures risk indicator”(SMRI) (analogous to the hazard index) on sufficiently similar mixtures linking exposure data with mixtures toxicology data. The methods are illustrated using pyrethroid mixtures occurrence data collected in child care centers (CCC) and dose‐response data examining acute neurobehavioral effects of pyrethroid mixtures in rats. Our method shows that the mixtures from 90% of the CCCs were sufficiently similar to the dose‐response study mixture. Using exposure estimates for a hypothetical child, the 95th percentile of the (weighted) SMRI for these sufficiently similar mixtures was 0.20 (i.e., where SMRI <1, less concern; >1, more concern).     

Taking Things Personally,and Publicising the Private: Encountering Erasure on the Frontlines of Academia

To understand the purpose of the Kunene hydro‐electic schemes in Angola one must examine the pattern of land settlement in Namibia established during the Herero‐German war of 1904–1908. At that time the White groups settled on the rich central pastoral land and also controlled the coast line. However the White south has three missing commodities which must be imported from the north: water, electricity, and labour. Thus it is the White groups who benefit most from the Kunene schemes. The profits from mining are accumulated in Johannesburg, New York, and London, while White mine workers receive high returns and Black workers receive low returns. The White farmers no longer face competition from the mines for water. The fishing and secondary industries receive relatively cheap power and water. Black farmers and herdsmen receive water, but the problem of irrigated farming in the ‘home‐lands’ has still to be solved.     

A POET IN PRISON

The True Confessions of an Albino Terrorist by Breyten Breytenbach. Mouroir by Breyten Breytenbach.     

Selective Maintenance in System Reliability with Random Costs of Repairing and Replacing the Components

In this paper we consider the problem of determining the optimum number of repairable and replaceable components to maximize a system's reliability when both, the cost of repairing the components and the cost of replacement of components by new ones, are random. We formulate it as a problem of non-linear stochastic programming. The solution is obtained through Chance Constrained programming. We also consider the problem of finding the optimal maintenance cost for a given reliability requirement of the system. The solution is then obtained by using Modified E-model. A numerical example is solved for both the formulations.     

Sexuality and the dual‐earner couple,part II: Beyond the baby years

This article reports results from two data sets testing predictions that a couple's sexual relationship suffers if the wife is employed, particularly if she is employed full time or high full time. A multiple‐theory framework was used, fusing the scarcity hypothesis, the enhancement hypothesis, and identity theory. The last suggests that an important individual difference variable, spouse role salience, should be related to a couples sexual functioning. In Study 1, data from the National Health and Social Life Survey were analyzed, focusing on 1,744 married persons. No significant differences in sexuality were found between women employed part, full, or high full time, nor between men employed full or high full time. In Study 2, data from the Wisconsin Maternity Leave and Health project were analyzed, focusing on 261 couples when they had a 4.5‐year‐old child. There were no differences between homemakers and women employed part, full, or high full time for several measures of sexual functioning. Neither were there differences between husbands employed full and high full time. More important were individual differences in spouse role salience.     

Some Correlates of Emotional Well-Being Among New England College Students

Abstract

In a questionnaire survey of New England college students, a large number of undergraduate men and women reported problems related to their personal, social, or academic adjustment. Given a list of 22 items described as “common concerns or feelings experienced by college students,” respondents were asked to rate the extent to which each item had been a problem for them in the past year. Most students (86%) reported having very much or somewhat of a problem with one or more items on the list. Pressure to do well in school, problems with weight control, anxiety, poor concentration and depression were among the most commonly reported concerns. The prevalence of these self-reported concerns and problems was found to be significantly associated with the respondents' sex, their perceptions of their health status, and academic standing.