Estimating reference ranges from stratified two-stage samples

We present methodology for estimating age-specific reference ranges by using data from two-stage samples. On the basis of the information obtained in the first stage, the initial sample is stratified and random subsamples are drawn from each stratum, where the selection probabilities in this second-stage sampling may be different across strata in the population. The variable for which the reference ranges are to be established is measured at the second phase. The approach involves maximum likelihood estimation of the parameters of the age-specific distributions and separate estimation of the population stratum probabilities. These are combined to yield estimates of the quantiles of interest. The issue of variance estimation for the estimated quantiles is also addressed. The methodology is applied to the estimation of reference ranges for a cognitive test score in a study of non-demented older Japanese-Americans.     

A Framework For The Study of Individual Behavior and Social Interactions

Recent work in economics has begun to integrate sociological ideas into the modeling of individual behavior. In particular, this new approach emphasizes how social context and social interdependences influence the ways in which individuals make choices. This paper provides an overview of an approach to integrating theoretical and empirical analysis of such environments. The analysis is based on a framework due to Brock and Durlauf (2001, forthcoming). Empirical evidence on behalf of this perspective is assessed and some policy implications are explored.     

Managing Risks in Multiple Online Auctions: An Options Approach*

The scenario of established business sellers utilizing online auction markets to reach consumers and sell new products is becoming increasingly common. We propose a class of risk management tools, loosely based on the concept of financial options that can be employed by such sellers. While conceptually similar to options in financial markets, we empirically demonstrate that option instruments within auction markets cannot be developed employing similar methodologies, because the fundamental tenets of extant option pricing models do not hold within online auction markets. We provide a framework to analyze the value proposition of options to potential sellers, option‐holder behavior implications on auction processes, and seller strategies to write and price options that maximize potential revenues. We then develop an approach that enables a seller to assess the demand for options under different option price and volume scenarios. We compare option prices derived from our approach with those derived from the Black‐Scholes model ( Black & Scholes, 1973 ) and discuss the implications of the price differences. Experiments based on actual auction data suggest that options can provide significant benefits under a variety of option‐holder behavioral patterns.     

“Are we a family or a business?” History and disjuncture in the urban American street gang

Theory and Society -     

Are You Sitting Comfortably Then We'll Begin: Three Gripping Policy Stories About Pension Reform

Throughout the 1990s, the issue of how to secure pension systems in the face of demographic change has been high on policy agendas in many countries. Yet, reforming pension systems has, more often than not, proved to be a particularly difficult and awkward political undertaking. The following article explores one of the many possible reasons why pension reform in Europe has been so arduous for the would-be reformers. After briefly reviewing some basic concepts and issues involved in reforming social security systems, the paper concentrates on how policy actors at international level have constructed the pension policy issue. Specifically, the paper reviews three pension reform policy stories. Each of the stories starts from differing assumptions, produces contradictory prognoses of the pension problem, and prescribes diverging policy solutions. Significantly, each policy story provides a normative vision of a 'good' pension reform. Thus, policy stories provide templates for producing plausible policy arguments in politiucal debates: yet, thay do so by weaving scientific knowledge, 'objective' fact and normative convictions about social welfare systems into a seamless rhetorical fabric. The final section, then, looks at the seams by analysing the more contentious assumptions of the different policy arguments.     

Risk of physical assault against school educators with histories of occupational and other violence: a case-control study

A case-control study design was used to investigate risks of work-related physical assault (PA) associated with a history of violent victimization among educators. A total of 6,469 state-licensed educators (Kindergarten - Grade 12) worked in the previous 12~months and were eligible to participate. Exposure data were collected from cases (reporting a PA event in previous 12 months, n=290) for the month before PA, and from controls (no work-related PA in previous 12 months; n=867) for a randomly selected working month. Odds ratios and 95% confidence intervals identified increased risks for educators with any prior history of work-related (17.3, 11.4-26.3) or non-work-related PA (2.0, 1.2-3.5). In addition, PA risk in the previous twelve months increased with the number of previous victimizations, and risk also increased for educators with histories of non-physical violence (work- and non work-related). The results present a compelling case for targeted interventions and further research.     

Design for Usability; practice-oriented research for user-centered product design

The Design for Usability project aims at improving the usability of electronic professional and consumer products by creating new methodology and methods for user-centred product development, which are feasible to apply in practice. The project was focused on 5 key areas: (i) design methodology, expanding the existing approach of scenario-based design to incorporate the interaction between product design, user characteristics, and user behaviour; (ii) company processes, barriers and enablers for usability in practice; (iii) user characteristics in relation to types of products and use-situations; (iv) usability decision-making; and (v) product impact on user behaviour. The project team developed methods and techniques in each of these areas to support the design of products with a high level of usability. This paper brings together and summarizes the findings.     

Assessment of futility in clinical trials

The term 'futility' is used to refer to the inability of a clinical trial to achieve its objectives. In particular, stopping a clinical trial when the interim results suggest that it is unlikely to achieve statistical significance can save resources that could be used on more promising research. There are various approaches that have been proposed to assess futility, including stochastic curtailment, predictive power, predictive probability, and group sequential methods. In this paper, we describe and contrast these approaches, and discuss several issues associated with futility analyses, such as ethical considerations, whether or not type I error can or should be reclaimed, one-sided vs two-sided futility rules, and the impact of futility analyses on power.     

Welfare Exit,Marriage, and Welfare Recidivism: A Reevaluation of Patterns of the 1980s and 1990s

We examine the relationship between marriage and welfare recidivism for women leaving a first welfare spell, using the 1979–2000 panels of the National Longitudinal Survey of Youth (NLSY). Previous studies have found that women who marry around the time of welfare exit have lower rates of welfare return than women who stay single. However, more marriages occur before or after welfare exit than occur at the time of welfare exit. We find that marriages that precede or follow welfare exit by more than 12 months are not associated with significantly lower rates of welfare return. We also confirm previous findings that marriages formed within a year of welfare exit are associated with reduced rates of welfare return. However, these reduced rates mostly indicate later welfare returns rather than fewer welfare returns. Overall, our findings indicate a much weaker association between marriage and welfare independence than has been previously reported for this time period.