VALIDATION OF A DIARY MEASURE OF CHILDREN'S PHYSICAL ACTIVITIES

This study compares levels of physical activity of 9–14-year-old children from a self-reported time diary with those measured using an accelerometer. Children (N = 92) wore an accelerometer for one weekend day and completed a 24-hour time diary for that day. The time children spent in moderate to vigorous physical activity from time diaries was moderately highly correlated with the measured results. Self-reported and objective measures of intensity were correlated, but the correlation varied substantially by activity and characteristics of the family. This study provides empirical evidence to support the validity of time-diary estimates when accelerometer data are not available.     

The Evolution of a Contested Concept: A Meta‐Analysis of Social Capital Definitions and Trends (1988–2006)*

This paper offers a meta‐analysis that traces the contested meaning and use of social capital in sociological research over the last 18 years by focusing on journal article definitions. We identify six common definitions in use that closely correspond to the original—and in some cases, independent—formulations offered by Hanifan, Putnam, Coleman, Bourdieu, and Granovetter. Drawing from Kuhnian theory, we contend that these definitions illuminate deep divisions between those who understand social capital as a normative “cure‐all” ( Portes 1998 )—in the tradition of Hanifan, Putnam, and Coleman —and those who view it as a resource—in the tradition of Bourdieu and Granovetter—that may be used to create or maintain social inequality. The transition of social capital from preparadigm to paradigm status may potentially involve an integration of these approaches, but this will require greater consideration of power and inequality on the part of normative theorists, who are currently dominating the debate.     

Quantifying costs of forecast errors: A case study of the warehouse environment

Our study evaluates the impact of forecast errors on organizational cost by simulating a labor-intensive warehouse environment using realistic cost data from a case study. Unlike past studies that measure forecast error in terms of forecast standard deviation, our study also considers the impact of forecast bias, and the complex interaction between these variables. Two cases of organizational cost curves are considered, with differing and asymmetric structures. Results find forecast bias to have a considerably greater impact on organizational cost than forecast standard deviation. Particularly damaging is a high bias in the presence of high forecast standard deviation. Although biasing the forecast in the least costly direction is shown to yield lower costs, sensitivity analysis shows that increasing bias beyond the optimum point rapidly increases costs. ‘Overshooting’ the optimal amount of bias appears to be more damaging than not biasing the forecast at all. Given that managers often deliberately bias their forecasts, this finding underscores the importance of having a good understanding of organizational cost structures before arbitrarily introducing bias. This finding also suggests that managers should exercise caution when introducing bias, particularly for forecasts that inherently have large errors. These findings have important implications for organizational decision making beyond the simulated warehouse, as high forecast errors are endemic to many labor-intensive organizations.     

Are you ready for ssmos?

While welfare reform altered entitlements, introduced time-limited benefits, and capped reimbursements for administrative costs, little was done to control service utilization by those who remain on welfare, or to realign the financial incentives and administrative infrastructure for the delivery of social services. This essay explores the advent of the Social Service Maintenance Organization and discusses the steps that social service agencies need to take to ready themselves for this altered system of service delivery. Without a thorough understanding of the way in which managed care delivery systems operate, as well as the sophisticated information systems and the financial resources necessary to assume risk, social service agencies will find themselves increasingly ill-equipped to meet the challenges of this new environment.     

Two-stage k-sample designs for the ordered alternative problem

In preclinical studies and clinical dose-ranging trials, the Jonckheere-Terpstra test is widely used in the assessment of dose-response relationships. Hewett and Spurrier (1979) presented a two-stage analog of the test in the context of large sample sizes. In this paper, we propose an exact test based on Simon's minimax and optimal design criteria originally used in one-arm phase II designs based on binary endpoints. The convergence rate of the joint distribution of the first and second stage test statistics to the limiting distribution is studied, and design parameters are provided for a variety of assumed alternatives. The behavior of the test is also examined in the presence of ties, and the proposed designs are illustrated through application in the planning of a hypercholesterolemia clinical trial. The minimax and optimal two-stage procedures are shown to be preferable as compared with the one-stage procedure because of the associated reduction in expected sample size for given error constraints.     

A framework for understanding collective leadership: The selective utilization of leader and team expertise within networks

To date, the dominant approach to leadership research assumes that all aspects of the leadership role within a team are embodied by a single individual. In the real world, however, this is rarely the case. Rather, multiple individuals within the team may serve as leaders in both formal and informal capacities, and the shifting of leadership responsibilities is often rooted in which individual's expertise is most relevant to the given problem. In the present effort, we add to the rapidly growing body of work that focuses on the distribution of the leadership role among multiple individuals. We have reviewed relevant extant literature and proposed an integrated framework for understanding the collective leadership process. Also, in developing this framework we have taken an information and expertise-based approach such that we propose that collective leadership, or the distribution of the leadership role, is a function of selectively utilizing the information or specialized expertise that individuals within the network possess. In reviewing the framework, 55 propositions with regard to the collective leadership process are outlined and suggestions for future research are provided.     

Stemming inequality? Employment and pay of female and minority scientists and engineers

When white men overwhelmingly dominated the science, technology, engineering, and mathematics (STEM) work force, the high pay in STEM occupations was a major source of gender and race inequality in the U.S. economy. As women, Blacks, and Latinos increasingly study STEM fields, new possibilities for achieving pay equality are opening. We test whether the reality matches the promise using two large data sets. Analysis of a five percent Public Use Microdata Sample (PUMS) of the 2000 Census and the 2001-06 American Community Surveys shows that women and minorities earn more, relative to comparable white men, in STEM than in non-STEM fields. This general pattern persists in analysis of a 1% sample of federal personnel records, which include better measures of work experience and education. Thus, federal efforts to increase the representativeness of the STEM workforce should increase pay equality in the economy by moving women and minorities into traditionally high-paying fields.     

Managerial hubris, firm expansion and firm performance: Evidence from China

Examining Chinese publicly traded firms from 2002 to 2005, we find managerial overconfidence to be positively correlated with the rate of firm expansion. In particular, overconfident managers tend to internally expand firms in an aggressive manner. We also find a negative, though not statistically significant, relationship between managerial overconfidence and M&A activity. Lastly, we examine the relationship between managerial overconfidence and firm performance, finding that managerial overconfidence decreases firm profitability due to overinvestment.