Nonparametric bootstrap of sample means of positive-definite matrices with an application to diffusion-tensor-imaging data analysis

This paper presents nonparametric two-sample bootstrap tests for means of random symmetric positive-definite (SPD) matrices according to two different metrics: the Frobenius (or Euclidean) metric, inherited from the embedding of the set of SPD metrics in the Euclidean set of symmetric matrices, and the canonical metric, which is defined without an embedding and suggests an intrinsic analysis. A fast algorithm is used to compute the bootstrap intrinsic means in the case of the latter. The methods are illustrated in a simulation study and applied to a two-group comparison of means of diffusion tensors (DTs) obtained from a single voxel of registered DT images of children in a dyslexia study.     

Reliability and Validity of the IPAQ-L in a Sample of Hong Kong Urban Older Adults: Does Neighborhood of Residence Matter?

This study examined reliability and validity of the Chinese version of the International Physical Activity Questionnaire-Long Form (IPAQ-LC) in Chinese seniors, including moderating effects of neighborhood walkability and socioeconomic status (SES) on reliability and validity. The IPAQ-LC was interviewer-administered (n = 96), accelerometer and 7-day walk-diary data were collected (n = 94), and the IPAC-LC was readministered (N = 92). Acceptable reliability was found for all measures of physical activity (PA) overall and across different types of neighborhood. Participants from highly walkable neighborhoods were more reliable at estimating walking for transport. Participants from low-SES areas were less reliable at estimating leisure-time PA and sitting but more reliable at estimating transport-related walking. IPAQ-LC walking was significantly related to light- but not moderate-intensity accelerometry-based PA. It was moderately to strongly related to a 7-day diary of walking. The data imply slow-paced walking, probably due to age, climate, and terrain. The findings suggest that the IPAQ-LC's reliability and validity are acceptable in Chinese seniors.     

The new wave of equality legislation: States move to create pay parity by banning inquiries into candidate's prior salary history

State‐by‐state survey on current laws prohibiting employers from inquiring into job candidate's prior salary history.     

School and school activity schedules affect the quality of family relations: a within-couple analysis

In this study, we focus on community resources – specifically, children's school and school activity schedules, or school resource fit (SRF) – as a contextual variable influencing family-role quality (FRQ) among employed parents of school-aged (grades K-12) children in a sample of 58 Boston-area couples (N=116). We found that SRF is a significant predictor of parent-role quality (PRQ) and marital-role quality (MRQ) for mothers, but not fathers. Further, for mothers, the relationship between SRF and each FRQ indicator was mediated by the other FRQ indicator. There was no evidence of crossover effects of one partner's SRF on the other partner's FRQ.     

Power in and around nonprofit boards: A neglected dimension of governance

In this article we propose five patterns of board governance based on the distribution of power in and around boards of nonprofit organizations. The typology proposed grew out of our findings in in-depth case studies in which the dispersion of power became the critical variable for making sense of the patterns of governance observed. These governance patterns were then incorporated into a survey of boards in the voluntary sector. We present the results of this latter phase of the research by focusing on the associations between the five patterns and the background characteristics of board members, organizational and environmental variables, and board and organizational effectiveness. The results of the study suggest that power is an important while largely neglected aspect of board governance in the not-for-profit sector.     

LOCATION OF THE OPTIMAL SAMPLING POINT FOR THE QUALITY ASSESSMENT OF CONTINUOUS STREAMS

The paper makes an appraisal of the most appropriate sampling point for situations where a single sample must be used to estimate the mean flow of a continuous stream during a set time interval. Taking ‘optimal’ to mean the point at which the estimation error variance is minimised, optimal sampling locations are obtained for constant, linear and exponential flow rates when the process variogram is assumed linear or exponential. Numerical results illustrate the significance of failing to sample at the optimal point.     

Class Inequalities in Education and Health: A Comparative Perspective

Class inequalities in education and health in several advanced capitalist countries are examined, distinguishing between three types of inequality: access to service, use of service and outcome. The evidence provided shows that the scope and complexity of class inequality increase as one moves from consideration of access to use and then to outcome. Hence the reduction of inequality of outcome is the most difficult. The evidence shows that inequality in all three areas is marked in all countries and it also suggests that reduction of inequalities over the years has been, at best, only slight. Continuation of present policies is unlikely to change the situation substantially. More egalitarian policies, however, appear unlikely to be pursued within the power constraints of advanced capitalist societies.     

Security systems and renewal processes

An interesting feature of successive inter-event times in a Poisson renewal process, when observed through a superimposed (possibly random) grid, can be interpreted as an extended form of the ‘inspection paradox’. Probabilistic measures are determined and an estimation and testing procedure is outlined which could be used to examine possible departure from randomness (Poisson form). The problem arose from study of security systems and the results have important applications in that field.