Smoothing parameter selection methods for nonparametric regression with spatially correlated errors

When spatial data are correlated, currently available data‐driven smoothing parameter selection methods for nonparametric regression will often fail to provide useful results. The authors propose a method that adjusts the generalized cross‐validation criterion for the effect of spatial correlation in the case of bivariate local polynomial regression. Their approach uses a pilot fit to the data and the estimation of a parametric covariance model. The method is easy to implement and leads to improved smoothing parameter selection, even when the covariance model is misspecified. The methodology is illustrated using water chemistry data collected in a survey of lakes in the Northeastern United States.     

Extreme behaviour for bivariate elliptical distributions

The authors examine the asymptotic behaviour of conditional threshold exceedance probabilities for an elliptically distributed pair (X, Y) of random variables. More precisely, they investigate the limiting behaviour of the conditional distribution of Y given that X becomes extreme. They show that this behaviour differs between regularly and rapidly varying tails.     

Development of Ego‐resiliency: Relations to Observed Parenting and Polymorphisms in the Serotonin Transporter Gene During Early Childhood

We used observed parenting behaviors, along with genetic variants and haplotypes of the serotonin transporter gene (SLC6A4), as predictors of children's ego‐resiliency during early childhood (N = 153). The quality of mothers' parenting was observed at 18 months of age, and mothers' reports of ego‐resiliency were collected at six time points from 18 to 84 months. Genetic data were collected at 72 months. Observed parenting was positively associated with initial levels of children's ego‐resiliency. Furthermore, although individual genetic variants of the serotonin transporter gene (LPR, STin2) were not associated with ego‐resiliency, the S10 haplotype (that combines information from these two variants) was negatively associated with initial levels of ego‐resiliency. Both parenting and serotonin genetic variation uniquely predicted children's ego‐resiliency, suggesting an additive effect of genetic and parental factors.     

The impact of macroeconomic conditions on income inequality

This paper analyzes the relationship between macroeconomic factors and the income distribution using data on equivalized disposable household income from the United Kingdom for 1961–99. We argue in favour of fitting a parametric functional form to the income distribution for each year, and then modeling the time series of model parameters in terms of the macroeconomic factors, as this better allows us to take into account non-stationarity in the time series. Estimates from models that relate income distribution parameters to cyclical variables in first differences (to account for non-stationarity) suggest that neither inflation nor unemployment have significant effects on income inequality. Compared to the commonly-used method of modelling the income shares directly, our approach indicates that there was no clear cut relationship between macroeconomic factors and the UK income distribution during the last third of the twentieth century.     

Issues in understanding quality volunteering in human services

Organisations providing human services are under increasing pressure to demonstrate quality from a range of sources such as new legislation and new requirements for government funding. Four dimensions for examining quality, derived from program evaluation theory, illustrated some of the contradictions surrounding these expectations. The research used a qualitative and grounded approach to exploring clients', volunteers' and coordinators' notions of quality service. The clients' and volunteers' perceptions of quality were highly experiential, related to the specific context and focussed on strong trusting personal relationships. Clients were also very conscious of their lack of power. Coordinators used a combination of approaches to try to satisfy the demands of clients, volunteers and bureaucracy.