The exact risk performance of a pre-test estimator in a heteroskedastic linear regression model under the balanced loss function

We examine the risk of a pre-test estimator for regression coefficients after a pre-test for homoskedasticity under the Balanced Loss Function (BLF). We show analytically that the two stage Aitken estimator is dominated by the pre-test estimator with the critical value of unity, even if the BLF is used. We also show numerically that both the two stage Aitken estimator and the pre-test estimator can be dominated by the ordinary least squares estimator when “goodness of fit” is regarded as more important than precision of estimation.     

A Weibull Regression Model with Gamma Frailties for Multivariate Survival Data

Frequently in the analysis of survival data, survival times within the same group are correlated due to unobserved co-variates. One way these co-variates can be included in the model is as frailties. These frailty random block effects generate dependency between the survival times of the individuals which are conditionally independent given the frailty. Using a conditional proportional hazards model, in conjunction with the frailty, a whole new family of models is introduced. By considering a gamma frailty model, often the issue is to find an appropriate model for the baseline hazard function. In this paper a flexible baseline hazard model based on a correlated prior process is proposed and is compared with a standard Weibull model. Several model diagnostics methods are developed and model comparison is made using recently developed Bayesian model selection criteria. The above methodologies are applied to the McGilchrist and Aisbett (1991) kidney infection data and the analysis is performed using Markov Chain Monte Carlo methods. This revised version was published online in July 2006 with corrections to the Cover Date.     

Risk/Benefit Assessments of Human Diseases: Optimum Dose for Intervention

A simple procedure is proposed in order to quantify the tradeoff between a loss suffered from an illness due to exposure to a microbial pathogen and a loss due to a toxic effect, perhaps a different illness, induced by a disinfectant employed to reduce the microbial exposure. Estimates of these two types of risk as a function of disinfectant dose and their associated relative losses provide information for the estimation of the optimum dose of disinfectant that minimizes the total expected loss. The estimates of the optimum dose and expected relative total loss were similar regardless of whether the beta-Poisson, log-logistic, or extreme value function was used to model the risk of illness due to exposure to a microbial pathogen. This is because the optimum dose of the disinfectant and resultant expected minimum loss depend upon the estimated slope (first derivative) of the models at low levels of risk, which appear to be similar for these three models at low levels of risk. Similarly, the choice among these three models does not appear critical for estimating the slope at low levels of risk for the toxic effect induced by the use of a disinfectant. For the proposed procedure to estimate the optimum disinfectant dose, it is not necessary to have absolute values for the losses due to microbial-induced or disinfectant-induced illness, but only relative losses are required. All aspects of the problem are amenable to sensitivity analyses. The issue of risk/benefit tradeoffs, more appropriately called risk/risk tradeoffs, does not appear to be an insurmountable problem.     

MULTISTAGE SAMPLING FOR RAW WOOL CHARACTERISTICS

The problem of evaluating the sampling variance of a mean when units are subsampled from a multistage sample is discussed. In particular, a specific problem arising in the sampling of wool where information on the identity of subsampled units is not available is dealt with by introducing a simple model to account for the variability in the unobserved numbers of observations within the multistage categories. Estimation aspects of the wool example are also dealt with.     

抗高温降滤失剂PAX的合成及性能

采用氧化还原体系以2-丙烯酰胺基-2-甲基丙磺酸(AMPS),丙烯酰胺(AM),等乙烯基单体为基本原料合成出了新型抗高温二元共聚物PAX系列处理剂。该降滤失剂在220℃的高温下及饱和盐水中具有良好的降滤失作用。     

Uniform asymptotic linearity in a regression parameter of a process based on a rank statistic

For X₁, …, X_N a random sample from a distribution F, let the process S^δ_N(t) be defined as where K²_N = σ^N_i=1(c_i ? c?)² and R x_i, + Δd, is the rank of X_i + Δd_i, among X₁ + Δd₁, …, X_N + Δd_N. The purpose of this note is to prove that, under certain regularity conditions on F and on the constants c_i and d_i, S^Δ_N (t) is asymptotically approximately a linear function of Δ, uniformly in t and in Δ, |Δ| ≤ C. The special case of two samples is considered.     

Leaving Science: Gender Differences in Career Continuity Following a Job Loss

This study investigates gender differences in the postdisplacement experience of nonacademic science and engineering (S&E) workers. Using a pooled sample created from the Displaced Worker Surveys conducted between 1994 and 2008, it finds that (1) this S&E work force is particularly vulnerable to job loss and potential career disruption; (2) displaced female S&E workers are more likely than comparable male workers to exit the work force, a gender difference that is conditional on and explained by marital and parental status; and (3) reemployed female S&E workers are also more likely to leave science for non‐S&E occupations, but this gender difference is limited to unmarried workers. A concluding section discusses the implications of these findings for interpreting gender differences in career outcomes.     

Biopower and Reproductive Loss

Extensive research indicates that mothers in particular grieve a variety of losses – miscarriage, stillbirth, ectopic pregnancy, induced abortions, newborn deaths – at all gestational stages, yet often find their grief invalidated. In turn, the lack of support or affirmation of these grief responses can be experienced as an exacerbation of the initial impact of death. This painful social silence that parents have expressed as part of their reproductive loss serves as the foundation for this paper, which explores both the strategic silences and discourses in the network of knowledges constituting reproductive loss in an era of biopower. The first section of the paper outlines the (bio)medicalization of the pregnant-unborn body, tracing this process through the deployment of sexuality that socialized fertility and the female body in the early eighteenth century. The second section discusses the responsibilization of the pregnant-unborn body through the technology of risk. Here I show how death infuses the discourse of state intervention in mortality rates, but as a strategic silence mobilizing the ethics of responsibility while never revealing the limits of biopower or the state's promise to foster, protect and enhance life. The third section turns to two discursive strategies tying the pregnant body and the foetal body in relation of responsibility: antenatal care and the reduction of perinatal mortality in late nineteenth- and early twentieth-century Western societies. These serve as more specific illustrations of how reproductive loss is taken up in politics of risk that remains in the biomedical understanding of pregnancy and childbirth today. I conclude with some reflections on the intercorporeality of becoming-unborn and becoming-death, connecting the struggle of parents bereaved by reproductive loss with a broader struggle to move beyond the biomedical control of life and death in an era of biopower.     

The order statistics of exponential,power function and pareto distributions and some applications

Some relations between the exponential, the Pareto and the Power function distributions and their order statistics are given. These relations are employed to obtain some characterization theorems of Pareto and Power distributions.     

A Worker's Personal Grief and Its Impact on Processing a Group's Termination

SUMMARY

This article deals with a worker struggling with a personal loss while simultaneously helping her group with the termination of a valued long term member. The focus is on the parallel grieving process and the resistance to mourning.