Tissue Dosimetry, Pharmacokinetic Modeling, and Interspecies Scaling Factors

Interspecies scaling factors (ISFs) are numbers used to adjust the potency factor (for example, the q1* for carcinogens or reference doses for compounds eliciting other toxic endpoints) determined in experimental animals to account for expected differences in potency between test animals and people. ISFs have been developed for both cancer and non-cancer risk assessments in response to a common issue: toxicologists often determine adverse effects of chemicals in test animals and then they, or more commonly risk assessors and risk managers, have to draw inferences about what these observations mean for the human population. This perspective briefly reviews the development of ISFs and their applications in health risk assessments over the past 20 years, examining the impact of pharmacokinetic principles in altering current perceptions of the ISFs applied in these health risk assessments, and assessing future directions in applying both pharmacokinetic and pharmacodynamic principles for developing ISFs.     

Taking (and Sharing Power): How Boards of Directors Can Bring About Greater Fairness for Dependent Stakeholders

One of the ways in which scholars have sought to broaden the discussion of the social responsibilities of corporations and their managers is through the development of the stakeholder concept. The primacy of shareholder interests in corporate‐governance processes and managerial action is, however, a myth that justifies all sorts of managerial self‐interest seeking and exploitation of particular stakeholder groups. What makes this myth particularly problematic—from the standpoint of fairness and corporate governance—is that not all nonshareholder stakeholders are equally situated with regard to their ability to secure fair treatment. In this article, I explore the ethical dimensions of board responsibilities to dependent stakeholder groups by first describing the differences between shareholders and nonshareholder stakeholders with regard to risk, examining why dependent stakeholders (stakeholders with legitimate and urgent claims, but no power) are particularly important from the standpoint of stakeholder risk, and discussing how stakeholder consultation might provide a partial fix to such problems. I will conclude with proposals for how boards can more faithfully discharge their ethical responsibilities to dependent stakeholder groups, and in so doing facilitate stakeholder involvement in corporate governance in ways that promote fairness in organization–stakeholder relationships.     

Sample design for observing classes of objects

We consider optimal sample designs for observing classes of objects. Suppose we will take a simple random sample of equal-sized sectors from a study population and observe the classes existing on these sectors. The classes might be many different things, for example, herbaceous plant species (in sampling quadrats), microinvertebrate species (in sampling cores), and side effects from a drug (in conducting medical trials). Under a nonparametric mixture model and data from a previous related study, we first estimate the optimal number of sample sectors of a given size. Then for negative binomial dispersions of individuals with a common aggregation parameter k, we consider the optimal size as well as number of sample sectors. A simple test exists to check our common k assumption and our optimal size method requires far less data than would be required by a grid method or other method which utilizes data from sample sectors of several different sizes.     

A robust process capability index

The existing process capability indices (PCI's) assume that the distribution of the process being investigated is normal. For non-normal distributions, PCI's become unreliable in that PCI's may indicate the process is capable when in fact it is not. In this paper, we propose a new index which can be applied to any distribution. The proposed indexC_f:, is directly related to the probability of non-conformance of the process. For a given random sample, the estimation of C_f boils down to estimating non-parametrically the tail probabilities of an unknown distribution. The approach discussed in this paper is based on the works by Pickands (1975) and Smith (1987). We also discuss the construction of bootstrap confidence intervals of C_f: based on the so-called accelerated bias correction method (BC _a:). Several simulations are carried out to demonstrate the flexibility and applicability of C_f:. Two real life data sets are analyzed using the proposed index.     

EVVMA and cusum control charts in the presence of correlation

The statistical properties of control charts are usually evaluated under the assumption that the observations from the process are independent. For many processes however, observations which are closely spaced in time will be correlated. This paper considers EWMA and CUSUM control charts for the process mean when the observations are from an AR(1) process with additional random error. This simple model may be a reasonable model for many processes encountered in practice. The ARL and steady state ARL of the EWMA and CUSUM charts are evaluated numerically using an integral equation approach and a Markov chain approach. The numerical results show that correlation can have a significant effect on the properties of these charts. Tables are given to aid in the design of these charts when the observations follow the assumed model.     

On the Alias Method for Generating Random Variables from a Discrete Distribution

The alias method of Walker is a clever, new, fast method for generating random variables from an arbitrary, specified discrete distribution. A simple probabilistic proof is given, in terms of mixtures, that the method works for any discrete distribution with a finite number of outcomes. A more efficient version of the table-generating portion of the method is described. Finally, a brief discussion on efficiency of the method is given. We believe that the generality, speed, and simplicity of the method make it attractive for use in generating discrete random variables.     

Design-based random permutation models with auxiliary information

We extend the random permutation model to obtain the best linear unbiased estimator of a finite population mean accounting for auxiliary variables under simple random sampling without replacement (SRS) or stratified SRS. The proposed method provides a systematic design-based justification for well-known results involving common estimators derived under minimal assumptions that do not require specification of a functional relationship between the response and the auxiliary variables.     

Parenting and child-caretaking among black men who have sex with men and associated sexual and reproductive health factors: a brief report

Abstract

The purpose of this exploratory study was to examine the prevalence of parenting and child-caretaking among a sample of black men who have sex with men (MSM), as well as associations between parenting roles and sexual and reproductive health (SRH) factors. Parenting and SRH data were derived from a survey of 199 black MSM. Nearly half of the sample reported being a father or father-figure (44.4%), almost a third indicated serving as caretaker of a child (29.1%), and one in five have a biological child (20.1%). Over half of the sample reported at least one of these three parenting/child-caretaking roles (52.5%). Two significant differences were observed for sexual health variables: men with biological children were significantly more likely to report using condoms inconsistently (55.0% vs. 35.7%, p = .026) and engaging in transactional sex work (36.8% vs. 21.0%, p = .041). Given the observed prevalence, parenting and child-caretaking among black MSM warrant further inquiry as factors that may influence SRH outcomes and care utilization. Services and interventions tailored to black MSM should consider these men’s potential roles and responsibilities as parents and caretakers of children.