Bivariate distributions of some ratios of independent noncentral chi-square random variables

The bivariate distributions of three pairs of ratios of in¬dependent noncentral chi-square random variables are considered. These ratios arise in the problem of computing the joint power function of simultaneous F-tests in balanced ANOVA and ANCOVA. The distributions obtained are generalizations to the noncentral case of existing results in the literature. Of particular note is the bivariate noncentral F distribution, which generalizes a special case of Krishnaiah*s (1964,1965) bivariate central F distribution. Explicit formulae for the cdf's of these distribu¬tions are given, along with computational procedures     

Reducing the Risk of Injury from Table Saw Use: The Potential Benefits and Costs of Automatic Protection

The use of table saws in the United States is associated with approximately 28,000 emergency department (ED) visits and 2,000 cases of finger amputation per year. This article provides a quantitative estimate of the economic benefits of automatic protection systems that could be designed into new table saw products. Benefits are defined as reduced health‐care costs, enhanced production at work, and diminished pain and suffering. The present value of the benefits of automatic protection over the life of the table saw are interpreted as the switch‐point cost value, the maximum investment in automatic protection that can be justified by benefit‐cost comparison. Using two alternative methods for monetizing pain and suffering, the study finds switch‐point cost values of $753 and $561 per saw. These point estimates are sensitive to the values of inputs, especially the average cost of injury. The various switch‐point cost values are substantially higher than rough estimates of the incremental cost of automatic protection systems. Uncertainties and future research needs are discussed.     

Risk Analysis for U.S. Offshore Wind Farms: The Need for an Integrated Approach

Wind power is becoming an increasingly important part of the global energy portfolio, and there is growing interest in developing offshore wind farms in the United States to better utilize this resource. Wind farms have certain environmental benefits, notably near‐zero emissions of greenhouse gases, particulates, and other contaminants of concern. However, there are significant challenges ahead in achieving large‐scale integration of wind power in the United States, particularly offshore wind. Environmental impacts from wind farms are a concern, and these are subject to a number of on‐going studies focused on risks to the environment. However, once a wind farm is built, the farm itself will face a number of risks from a variety of hazards, and managing these risks is critical to the ultimate achievement of long‐term reductions in pollutant emissions from clean energy sources such as wind. No integrated framework currently exists for assessing risks to offshore wind farms in the United States, which poses a challenge for wind farm risk management. In this “Perspective”, we provide an overview of the risks faced by an offshore wind farm, argue that an integrated framework is needed, and give a preliminary starting point for such a framework to illustrate what it might look like. This is not a final framework; substantial work remains. Our intention here is to highlight the research need in this area in the hope of spurring additional research about the risks to wind farms to complement the substantial amount of on‐going research on the risks from wind farms.     

Whither Risk Assessment: New Challenges and Opportunities a Third of a Century After the Red Book

Six multi‐decade‐long members of SRA reflect on the 1983 Red Book in order to examine the evolving relationship between risk assessment and risk management; the diffusion of risk assessment practice to risk areas such as homeland security and transportation; the quality of chemical risk databases; challenges from other groups to elements at the core of risk assessment practice; and our collective efforts to communicate risk assessment to a diverse set of critical groups that do not understand risk, risk assessment, or many other risk‐related issues. The authors reflect on the 10 recommendations in the Red Book and present several pressing challenges for risk assessment practitioners.     

Employment-based health benefits: analysis of the April 1993 Current Population Survey

The April 1993 CPS differs from the March 1993 CPS in a number of respects. The April 1993 CPS supplement surveys only workers, whereas the March CPS examines the noncash benefits received by all Americans. The April CPS asks workers about health coverage in the week in which the questions were fielded, whereas the March CPS asks about coverage in the preceding year. In April 1993, there were 112.5 million civilian American workers between the ages of 18 and 64 with jobs. Eighty-two million (73 percent) of them worked for an employer that sponsored a health insurance plan, and 65 million (58 percent of all workers) participated in their employer's health plan. About one-third of workers at firms with fewer than 10 employees had employers who offer health benefits; about one-quarter of all of the workers in these firms participated in their employer's plan. Conversely, 94 percent of workers at firms with more than 1,000 employees had an employer who sponsored health benefits, and over 77 percent of these workers participated in their employer's plan. There are 16.5 million American workers whose employers sponsored health benefits but who did not participate in these benefits. Over one-half of these workers (8.5 million) chose not to be covered. Another 36 percent of these workers (5.9 million) did not participate because they were ineligible or denied coverage. Over 66 percent of the ineligible workers did not participate because they were part-time, contract, or temporary workers. Another 26 percent had not yet completed a probationary period. Among the reasons that those who chose not to participate in their employer's coverage, the vast majority (75 percent) stated they were covered by another health care plan. Twenty-nine percent stated that they chose not to purchase coverage because it was too costly or that they did not need or want the coverage. In 1993, there were 16.7 million workers with no health insurance coverage. The vast majority of these workers (95 percent) were employed by private employers. Sixty-six percent of the workers with no health insurance coverage were self-employed or worked for firms with fewer than 100 employees.     

Testing Fair Wage Theory

Fairness considerations often are invoked to explain wage differences that appear unrelated to worker characteristics or job conditions, but non-experimental tests of fair wage models are rare because market data rarely permit researchers to measure individual workers’ productivity and its value. We use data from the baseball labor market to address this problem, and find no support for fair wage theory. We do find, however, that fairness premia can be illusory: Wages appear to incorporate fairness premia in regressions that control for variation in individuals’ physical output, but such premia evaporate when the value of that output is held constant.

Employment expectations and the costs of migration

This paper analyses the employment and migration expectations and the perceived costs and returns to migration of a group of workers who have recently lost their employment due to the closure of the major employer in a small rural community. A model of migration decision-making is developed and data relating to this are presented. The contingent valuation approach is used to estimate the losses associated with a move away from the area. The results of an attempt to estimate the complete migration model are described. Finally, the likely approach to the issue of migration under these particular circumtances is discussed.     

Community councils as a medium for public participation: a case study in Grampian region

Planning authorities in Scotland are obliged to consult the public before finalising policies and proposals to be included in their development plans. Community councils are intended to operate as ‘the voice of a neighbourhood’ and this paper analyses an attempt by a regional planning authority to use community councils as a vehicle for consulting the public in the preparation of a structure plan for a rural area. The paper concludes that the attempt was unsuccessful because the community councils were not clear about the role they were expected to play; nor were they adequately prepared for their role. The authors believe, however, that the involvement of community councils has potential for promoting greater public participation in the preparation of development plans.     

Psychosocial correlates and depression in Vietnamese adolescents

This paper reports findings on depression in a sample of 38 Vietnamese adolescents. Hierarchical regression analysis was conducted to examine the empirical use of psychosocial variables and stressful life event measures in predicting depression. Self-esteem (Esteem) and SLEs scales were entered in blocks and explained for 68 percent of the total variance in depression (CES-D scale). Esteem accounts for 30 percent of the overall variance. The SLE block contributes another 39 percent above and beyond in the prediction of depression. Death, PTSD, and Peer stress scales were significant predictors (p<.01). The mean CES-D depression score was 16.32 (SD=10.95). A cutoff score of 16 was used to classify those adolescents who were depressed from those who were not depressed (Radloff, 1977).     

Expressing imprecision in probabilistic knowledge

Summary The representation of imprecise knowledge in probabilistic expert systems is investigated. It is argued that Bayesian statistics offers a multitude of models and methods that may be employed to express probabilistic knowledge by first and second order probability distributions. Distributions offer a much richer repertoire to express uncertainty that point probabilities. Special attention is payed to Dirichletian weights of evidence in discrete systems and to predictons and inverse predictions in linear regression. Approximate methods for non-conjugate distributions and for incomplete data are discussed. An important property of imprecision in complex systems is that it explodes rapidly when the conclusions are derived from long chains of premises. Thus, imprecision is a pruning criterion is a pruning criterion in complex knowledge systems. This research was supported by the Fonds zur F?rderung der wissenschftlichen Forschung, Vienna.