Revisiting retesting in the estimation of proportions by group testing

In the estimation of a proportion p by group testing (pooled testing), retesting of units within positive groups has received little attention due to the minimal gain in precision compared to testing additional units. If acquisition of additional units is impractical or too expensive, and testing is not destructive, we show that retesting can be a useful option. We propose the retesting of a random grouping of units from positive groups, and compare it with nested halving procedures suggested by others. We develop an estimator of p for our proposed method, and examine its variance properties. Using simulation we compare retesting methods across a range of group testing situations, and show that for most realistic scenarios, our method is more efficient.     

Dynamic Graphics for Exploring Spatial Data with Application to Locating Global and Local Anomalies

We explore the application of dynamic graphics to the exploratory analysis of spatial data. We introduce a number of new tools and illustrate their use with prototype software, developed at Trinity College, Dublin. These tools are used to examine local variability—anomalies—through plots of the data that display its marginal and multivariate distributions, through interactive smoothers, and through plots motivated by the spatial auto-covariance ideas implicit in the variogram. We regard these as alternative and linked views of the data. We conclude that the most important single view of the data is the Map View: All other views must be cross-referred to this, and the software must encourage this. The view can be enriched by overlaying on other pertinent spatial information. We draw attention to the possibilities of one-many linking, and to the use of line-objects to link pairs of data points. We draw attention to the parallels with work on Geographical Information Systems.     

The Exchange of Publications; An Alternative to Acquisitions

Abstract

In March 2001 the Canadian National Site Licensing Project (CNSLP) enabled the University of Saskatchewan Library to add over seven hundred electronic titles to its journal collection. The CNSLP titles introduced a critical mass of electronic journals to library patrons, offering a complex and intriguing range of supplementary content and a transformation of the experience of reading scientific journals. This article reports on the plug-ins and add-ons required to access supplementary content in the CNSLP electronic journals and explores the implications of supplementary content for readers. Serials Review 2003; 29:103–116.     

Some efficient random imputation methods

Imputation methods that assign a selection of respondents’ values for missing i tern nonresponses give rise to an addd,tional source of sampling variation, which we term imputation varLance , We examine the effect of imputation variance on the precision of the mean, and propose four procedures for sampling the rEespondents that reduce this additional variance. Two of the procedures employ improved sample designs through selection of respc,ndents by sampling without replacement and by stratified sampl;lng. The other two increase the sample base by the use of multiple imputations.     

Meeting summary--cell biology of Parkinson's disease and related neurodegenerative disorders

Parkinsonian disorders (idiopathic Parkinson's disease and clinically similar disorders) are characterized by impaired movements caused by the degeneration of brain centers involved in regulating normal and smooth movements of the body and its extremities. The mechanisms that cause such degeneration are unknown. This Perspective summarizes research described at a meeting held in June 2003, which was organized by the National Institute of Neurological Disorders and Stroke and the National Institute on Aging to provide an update on recent advances in the cell biology of parkinsonian disorders.     

Application of commercial software to the classification of suicide cases: a brief report

Mosaic Profiler software was used to classify suicide and open verdict cases during 1996 to 1998 in England and within England, for the London and the North West regions. The classification system was based on the socioeconomic characteristics of the last place of residence of the cases at the level of postcode. The results highlighted that deprived areas and areas that contain elderly population or those areas that suffer from lack of social cohesion are overrepresented, whereas affluent areas are underrepresented. All of these, although in the larger scale, seem to support the results of other studies. Nevertheless, more studies would be required before one can fully evaluate the application of the Mosaic Profiler in the field of spatial epidemiology.     

Editorial: South of the Border Seen Close Up

Population and Environment -