Testing Time Series for Nonlinearity

The technique of surrogate data analysis may be employed to test the hypothesis that an observed data set was generated by one of several specific classes of dynamical system. Current algorithms for surrogate data analysis enable one, in a generic way, to test for membership of the following three classes of dynamical system: (0) independent and identically distributed noise, (1) linearly filtered noise, and (2) a monotonic nonlinear transformation of linearly filtered noise.We show that one may apply statistics from nonlinear dynamical systems theory, in particular those derived from the correlation integral, as test statistics for the hypothesis that an observed time series is consistent with each of these three linear classes of dynamical system. Using statistics based on the correlation integral we show that it is also possible to test much broader (and not necessarily linear) hypotheses.We illustrate these methods with radial basis models and an algorithm to estimate the correlation dimension. By exploiting some special properties of this correlation dimension estimation algorithm we are able to test very specific hypotheses. Using these techniques we demonstrate the respiratory control of human infants exhibits a quasi-periodic orbit (the obvious inspiratory/expiratory cycle) together with cyclic amplitude modulation. This cyclic amplitude modulation manifests as a stable focus in the first return map (equivalently, the sequence of successive peaks).     

When Can Scientific Studies Promote Consensus Among Conflicting Stakeholders?

While scientific studies may help conflicting stakeholders come to agreement on a best management option or policy, often they do not. We review the factors affecting trust in the efficacy and objectivity of scientific studies in an analytical‐deliberative process where conflict is present, and show how they may be incorporated in an extension to the traditional Bayesian decision model. The extended framework considers stakeholders who differ in their prior beliefs regarding the probability of possible outcomes (in particular, whether a proposed technology is hazardous), differ in their valuations of these outcomes, and differ in their assessment of the ability of a proposed study to resolve the uncertainty in the outcomes and their hazards—as measured by their perceived false positive and false negative rates for the study. The Bayesian model predicts stakeholder‐specific preposterior probabilities of consensus, as well as pathways for increasing these probabilities, providing important insights into the value of scientific information in an analytic‐deliberative decision process where agreement is sought. It also helps to identify the interactions among perceived risk and benefit allocations, scientific beliefs, and trust in proposed scientific studies when determining whether a consensus can be achieved. The article provides examples to illustrate the method, including an adaptation of a recent decision analysis for managing the health risks of electromagnetic fields from high voltage transmission lines.     

Risk Factors,Parental Communication,Self and Peers’ Beliefs as Predictors of Condom Use Among Female Adolescents Attending Family Planning Clinics

This study examined the impact of risk factors, self and peers’ beliefs, and parental communication on condom use among 290 female adolescents who attended family planning clinics. The major findings showed that in addition to risk factors, self and peer beliefs about condom use and parental communication about birth control predicted actual condom use. Implications for social workers about the importance of encouraging communication between adolescents and their parents are discussed.     

Judged Terror Risk and Proximity to the World Trade Center

In November 2001, a nationally representative sample of Americans (N = 973, ages 13–88), queried via WebTVs at home, judged the probability of five terror-related events (e.g., being injured in an attack) and three “routine” risks (e.g., being a victim of other violent crime), in the following 12 months. Judgments of terror risks, but not routine risks, were related to whether respondents were within 100 mi of the World Trade Center. This relationship was found only in the following demographic groups, and not their complements: men, adults, whites, and Republicans. These differential responses to risk have both theoretical and policy implications.     

Weak ties and the core discussion network: Why people regularly discuss important matters with unimportant alters

Researchers have paid increasing attention to the core discussion network, the set of friends and family people turn to when discussing important matters. For nearly thirty years, social network researchers have argued that the network is composed of ego's closest or most important alters. This assumption, however, has not been tested empirically. Using original data on an online representative quota survey of 2000 respondents, I find that 45% of the core discussion network is composed of people whom respondents do not consider important to them. In fact, the core discussion network includes doctors, co-workers, spiritual leaders, and other alters whom ego confides in without feeling emotionally attached to. I examine what respondents consider important matters and why they approach weak ties to discuss these. Placing emphasis on the process through which ego mobilizes alters, I develop two theoretical perspectives, which focus on how people identify those appropriate to a topic and how they respond to opportunities in interactional contexts. Findings suggest that ego discusses important matters with non-close alters at times because they are known to be knowledgeable (targeted mobilization) and at times because they are available when important issues arise (opportune mobilization). Results suggest that recent findings about changes in the core discussion network of Americans are consistent with several different possibilities about the nature of strong ties, including those in which there has been no change at all.     

Ethnography Upgraded

Qualitative Sociology - The basic practice of ethnography has essentially remained unchanged in hundreds of years. How has online life changed things? I contrast two transformative inventions, the...     

Statistical inference in dynamic panel data models

Anderson and his collaborators have made seminal contributions to inference with instrumental variables and to dynamic panel data models. We review these contributions and the extensive economic and statistical literature that these contributions spawned. We describe our recent work in these two areas, presenting new approaches to (a) making valid inferences in the presence of weak instruments and (b) instrument and model selection for dynamic panel data models. Both approaches use empirical likelihood and resampling. For inference in the presence of weak instruments, our approach uses model averaging to achieve asymptotic efficiency with strong instruments but maintain valid inferences with weak instruments. For instrument and model selection, our approach aims at choosing valid instruments that are strong enough to be useful.     

Big knickers: A brief history of the world in 10 1/2 minutes

From the notion that our ideas of space are defined by their margins, this paper explores some of the social, symbolic and cultural means commonly used in particular contexts to determine both the definition of these perimeters and the various competing social structures implicit in their maintenance and function, or otherwise. In addition to first-hand accounts and ethnographies, the work draws on sources ranging from literature and journalism to architecture and social anthropology, all presented in terms of the author's long established, and much published, approach to SCOS events and the broader discontinuities of life in general. So, for example, the title of his proposed piece contains an oblique yet knowing reference to theories of relativity in that no matter how light the text may be, or lacking in gravity, it cannot easily be described within the space of ten and a half minutes.     

Displacement,caregiving, and the ecological system of youth in foster care: a theoretical perspective

Children involved in the child welfare (i.e., foster care) system are at a greater risk for numerous negative outcomes in adolescence and adulthood (e.g., lower educational attainment, higher risk for a criminal record). For children in foster care who experience placement disruption (i.e., removed from a foster home and placed in another nonpermanent placement), the risks significantly increase. Informed by the ecological systems model, the authors propose a theoretical perspective to explain the unique aspects of a foster child’s development and discuss how this framework informs child welfare practice and intervention for foster children at risk for placement disruption. This perspective has the potential to provide a framework that has implications for foster caregivers and child welfare professionals and to inform future policies.     

Action‐Oriented Research: Strategies for Engaged Scholarship

Action‐oriented research is a methodological approach for doing collaborative research with practitioners and community partners that can inform practice, programs, community development, and policy while contributing to the scientific knowledge base. This article discusses how family scholars can use action‐oriented research to work together with community partners to address their need for useful information about their practices and programs. We present some practical strategies that can help guide the action‐oriented research process including how to develop collaborative relationships with community partners; suggestions for determining sound, action‐oriented research questions; guidelines for selecting and implementing appropriate research designs; and considerations regarding data collection and the dissemination of findings.