A robust QTL mapping procedure

In quantitative trait linkage studies using experimental crosses, the conventional normal location-shift model or other parameterizations may be unnecessarily restrictive. We generalize the mapping problem to a genuine nonparametric setup and provide a robust estimation procedure for the situation where the underlying phenotype distributions are completely unspecified. Classical Wilcoxon–Mann–Whitney statistics are employed for point and interval estimation of QTL positions and effects.     

Maternal Lifetime Trauma Exposure,Prenatal Cortisol,and Infant Negative Affectivity

Little research has examined the impact of maternal lifetime trauma exposure on infant temperament. We examined associations between maternal trauma history and infant negative affectivity and modification by prenatal cortisol exposure in a sociodemographically diverse sample of mother–infant dyads. During pregnancy, mothers completed measures of lifetime trauma exposure and current stressors. Third‐trimester cortisol output was assessed from maternal hair. When infants were 6 months old, mothers completed the Infant Behavior Questionnaire‐Revised. In analyses that controlled for infant sex and maternal age, education, race/ethnicity, and stress during pregnancy, greater maternal trauma exposure was associated with increased infant distress to limitations and sadness. Higher and lower prenatal cortisol exposure modified the magnitude and direction of association between maternal trauma history and infant rate of recovery from arousal. The association between maternal trauma history and infant distress to limitations was somewhat stronger among infants exposed to higher levels of prenatal cortisol. The analyses suggested that maternal lifetime trauma exposure is associated with several domains of infant negative affectivity independently of maternal stress exposures during pregnancy and that some of these associations may be modified by prenatal cortisol exposure. The findings have implications for understanding the intergenerational impact of trauma exposure on child developmental outcomes.     

The Equivalence of Neyman Optimum Allocation for Sampling and Equal Proportions for Apportioning the U.S. House of Representatives

We present a surprising though obvious result that seems to have been unnoticed until now. In particular, we demonstrate the equivalence of two well-known problems—the optimal allocation of the fixed overall sample size n among L strata under stratified random sampling and the optimal allocation of the H = 435 seats among the 50 states for apportionment of the U.S. House of Representatives following each decennial census. In spite of the strong similarity manifest in the statements of the two problems, they have not been linked and they have well-known but different solutions; one solution is not explicitly exact (Neyman allocation), and the other (equal proportions) is exact. We give explicit exact solutions for both and note that the solutions are equivalent. In fact, we conclude by showing that both problems are special cases of a general problem. The result is significant for stratified random sampling in that it explicitly shows how to minimize sampling error when estimating a total T_Y while keeping the final overall sample size fixed at n; this is usually not the case in practice with Neyman allocation where the resulting final overall sample size might be near n + L after rounding. An example reveals that controlled rounding with Neyman allocation does not always lead to the optimum allocation, that is, an allocation that minimizes variance.     

Respiratory illness in Saskatoon infants: The impact of housing and neighbourhood characteristics

Respiratory illness is an important childhood illness and a significant cause of infant mortality. This study examined the relationship between neighbourhood level variables and rates of respiratory illness for children less than 2 years of age, born in Saskatoon between 1992 and 1994. Rates of respiratory illness, as measured by proportion of children hospitalized and frequency of hospitalization and ambulatory visits to physicians, were higher among infants living in socially disadvantaged neighbourhoods. Multivariate predictive models for rates of respiratory illness support the research hypothesis that housing characteristics, in the presence of other neighbourhood characteristics, have a significant impact on determining the rates of respiratory illness among Saskatoon children.     

Person, Perception, and Place: What Matters to Health and Quality of Life

Interest in understanding how characteristics associated with where people live, in addition to the characteristics of the people themselves, affect health outcomes has risen sharply in recent years. While much of the research examining this question focus on teasing apart effects of place and individual on outcomes, less attention has been paid to examining how individuals’ perceptions of where they live may provide some clues to better understanding the influence of place on outcomes. We present findings from analysis undertaken that incorporate the subjective responses of individuals, residing in three socially contrasting neighbourhoods, to their local environment. Our first question addressed whether perceptions related to neighbourhood and city of residence matter to self rated health and quality of life independent of individual characteristics, while the second question examined whether the perceptions and individual characteristics are modified by the neighbourhood socio-economic context. Our results show that perceived neighbourhood characteristics, in addition to individual sociodemographic factors, are significant correlates of self rated health and quality of life. Moreover, we show that the type of perceived neighbourhood characteristics and the magnitude of their influence on self rated health and quality of life vary depending on whether they live in high- versus low-socioeconomic status neighbourhoods.

The Next Generation of Collective Action Research

The articles presented in this volume describe part of a new generation of interest and vigor in the social psychological study of collective action. This new wave builds nicely on the foundation set by social identity, self-categorization, and relative deprivation theories but also introduces a number of important innovative perspectives and variables. In this commentary, I review some of these expansions and additions, raise a number of conceptual concerns that arise out of these new directions, and discuss more generally some novel and important directions that emerge from the work presented in the volume and in other recent work on collective action.     

Uncertain Benefits Estimates for Reductions in Fine Particle Concentrations

The Environmental Protection Agency's (EPA's) estimates of the benefits of improved air quality, especially from reduced mortality associated with reductions in fine particle concentrations, constitute the largest category of benefits from all federal regulation over the last decade. EPA develops such estimates, however, using an approach little changed since a 2002 report by the National Research Council (NRC), which was critical of EPA's methods and recommended a more comprehensive uncertainty analysis incorporating probability distributions for major sources of uncertainty. Consistent with the NRC's 2002 recommendations, we explore alternative assumptions and probability distributions for the major variables used to calculate the value of mortality benefits. For metropolitan Philadelphia, we show that uncertainty in air quality improvements and in baseline mortality have only modest effects on the distribution of estimated benefits. We analyze the effects of alternative assumptions regarding the value of reducing mortality risk, whether the toxicity is above or below the average for fine particles, and whether there is a threshold in the concentration‐response relationship, and show these assumptions all have large effects on the distribution of benefits.     

Federated searching and usability testing: Building the perfect beast

With the ubiquity of federated search tools as viable solutions for students and researchers to search across external sources and internal repositories, users have become more sophisticated in their application of this technology. With the goal of optimizing the user experience of its newly introduced federated search offering, Endeavor Information Systems employed usability testing to gain insights into the critical requirements of librarians and information professionals for this solution. The results of this analysis, conducted in concert with market research and customer focus groups, and their relevance to Endeavor's federated search technology are the focus of this article.     

The power functions of the likelihood ratio tests for a simply ordered trend in normal means

Likelihood ratio tests for the homogeneity of k normal means with the alternative restricted by an increasing trend are considered as well as the likelihood ratio tests of the null hypothesis that the means satisfy the trend. While the work is primarily a survey of results concerning the power functions of these tests, the extensions of some results to the case of not necessarily equal sample sizes are presented. For the case of known or unknown population variances, exact expressions are given for the power functions for k=3,4, and approximations are discussed for larger k. The topics of consistency, bias and monotonicity of the power functions are included. Also, Bartholomew's conjectures concerning minimal and maximal powers are investigated, with results of a new numerical study given.