Further approximate pearson percentage points and Cornish-Fisher

A set of 19-point rational fraction approximants for Pearson distributions at levels a = 0.025, 0.25, 0.50, 0.75, and 0.975 is added to a previous study (Biometrika, 1979). The relation to a Cornish-Fisher expansion is discussed and advice proffered on interpolation for a new deviate or new level.     

The Impact of Causal Ambiguity on Competitive Advantage and Rent Appropriation

We seek to develop the conceptual and practical understanding of causal ambiguity. Specifically we extend current thinking by setting out three types of causal ambiguity, based on whether firm resources are perceived to display linkage and/or characteristic ambiguity, and by examining for each type the impact of causal ambiguity on the sustainability of competitive advantage and on rent appropriation. We highlight the difficulties decision‐makers face when they perceive ambiguity and finally we explore some implications of ambiguity with respect to resource‐creation processes.     

Modeling, Evaluation, and Methodology in the New Century

The modern world has influenced the approach to empirical modeling and consequently the approach to methodology in general. The question of whether to base a model on an economic theory is easier when several models can be constructed, but an empirical evaluation analysis is required. Starting with a widely specified model and using a reduction procedure is currently a popular process; it is unclear if the reduction should be to a single or to a few alternatives. New methodologies are required for conditional predictive distributions, which are the models of the future.     

Modeling developmental data using U-shaped threshold dose-response curves

This paper develops threshold models for developmental toxicity data. The distinguishing feature of these threshold models is their flexibility in modeling data below threshold with a U-shaped function if the data warrants. The method is applied to actual data from a developmental study which exhibits U-shaped behavior in early dose groups. Results from a simulation study demonstrate the flexibility of the threshold model to pick up on U-shaped trends in the data. In addition, the simulation study reveals important considerations in design of developmental studies.     

Independent fostering agencies uncovered: the findings of a national study

This paper presents the findings of a survey of independent fostering agencies (IFAs) in England, Scotland and Wales. Information was gathered about their operational arrangements, services, fees, staffing, foster carers and the children and young people in placement. This information is supplemented by an earlier evaluation of one large English IFA and by reference to the available relevant literature. The expansion of the IFAs has been generally greeted with hostility by local authority managers because of what is perceived as the loss of foster carers to the independent sector, the costs of the IFAs and their position outside the public welfare sector. This paper questions the validity of these views following an examination of the status of the agencies, the background of their foster carers and the circumstances surrounding the placements of the children and young people. It concludes by identifying gaps in our knowledge and areas for future research.     

A Parametric Model for Detecting Hormetic Effects in Developmental Toxicity Studies

Hormetic effects have been observed at low exposure levels based on the dose-response pattern of data from developmental toxicity studies. This indicates that there might actually be a reduced risk of exhibiting toxic effects at low exposure levels. Hormesis implies the existence of a threshold dose level and there are dose-response models that include parameters that account for the threshold. We propose a function that introduces a parameter to account for hormesis. This function is a subset of the set of all functions that could represent a hormetic dose-response relationship at low exposure levels to toxic agents. We characterize the overall dose-response relationship with a piecewise function that consists of a hormetic u-shape curve at low dose levels and a logistic curve at high dose levels. We apply our model to a data set from an experiment conducted at the National Toxicology Program (NTP). We also use the beta-binomial distribution to model the litter response data. It can be seen by observing the structure of these data that current experimental designs for developmental studies employ a limited number of dose groups. These designs may not be satisfactory when the goal is to illustrate the existence of hormesis. In particular, increasing the number of low-level doses improves the power for detecting hormetic effects. Therefore, we also provide the results of simulations that were done to characterize the power of current designs in detecting hormesis and to demonstrate how this power can be improved upon by altering these designs with the addition of only a few low exposure levels.     

Multigenerational Interactions in Black Middle Class Wealth and Asset Decision Making

Traditional comparisons of wealth and asset attainment between Blacks and Whites suggest disproportionate outcomes; yet are limited in capturing the intrinsic factors that influence the decision-making process. This study examines the multigenerational interactions and influences that shape Black middle-class wealth and asset decision-making. Twenty-nine in depth interviews with Black middle-class families from three metropolitan cities were completed to provide insight into the factors that influence their economic decision-making. Results indicate Black multigenerationalism plays a significant and unique role in the understanding of contemporary wealth and asset decision making for Black middle-class families, including: (a) the desire for “safe” economic decision-making by parents, (b) the absence of a formal, multigenerational discourse, and (c) the absence of early, alternative economic knowledge.