Improvement of Highway Safety I: Identification of Causal Factors Through Fault-Tree Modeling1

As the first article of a two-part series, the purpose of this paper is to examine the functional factors that contribute to automobile accident occurrence and to model the causation structure in the form of a fault-tree. The fault-tree model provides an intuitive framework for qualitatively decomposing possible pathways to accident occurrence. Fault-tree analysis also provides a statistical representation of how interacting driver, vehicle, and environmental factors contribute to the likelihood of automobile accident occurrence. The application of this model facilitates pinpointing those factors that most contribute to accident causation and subsequently enables the identification and comparison of potential crash avoidance technologies.     

Bayesian palaeoclimate reconstruction

Summary.  We consider the problem of reconstructing prehistoric climates by using fossil data that have been extracted from lake sediment cores. Such reconstructions promise to provide one of the few ways to validate modern models of climate change. A hierarchical Bayesian modelling approach is presented and its use, inversely, is demonstrated in a relatively small but statistically challenging exercise: the reconstruction of prehistoric climate at Glendalough in Ireland from fossil pollen. This computationally intensive method extends current approaches by explicitly modelling uncertainty and reconstructing entire climate histories. The statistical issues that are raised relate to the use of compositional data (pollen) with covariates (climate) which are available at many modern sites but are missing for the fossil data. The compositional data arise as mixtures and the missing covariates have a temporal structure. Novel aspects of the analysis include a spatial process model for compositional data, local modelling of lattice data, the use, as a prior, of a random walk with long-tailed increments, a two-stage implementation of the Markov chain Monte Carlo approach and a fast approximate procedure for cross-validation in inverse problems. We present some details, contrasting its reconstructions with those which have been generated by a method in use in the palaeoclimatology literature. We suggest that the method provides a basis for resolving important challenging issues in palaeoclimate research. We draw attention to several challenging statistical issues that need to be overcome.     

Transnational social work: using a wraparound model

In this article, we explore the wraparound approach of service delivery as a model for transnational social work. The wraparound model, used primarily within community‐based children's mental health services and child protection initiatives, has been effective when planning services for clients and their families with complicated needs, whose care has to be provided within a multiple provider context. Most social work is delivered nationally or internationally rather than trans‐nationally. In the article we outline how the model could be structured to meet the particular needs of transmigrants, including the involvement of NGOs and INGOs, and identify key obstacles and limitations.     

Mixing patterns between age groups in social networks

We present a method for estimating transmission matrices that describe the mixing and the probability of infection between age groups. Transmission matrices can be used to estimate age-dependent forces of infection in age-structured, compartmental models for the study of infectious diseases. We analyze the social network generated by the synthetic population of Portland and extract mixing patterns. Our results show that the mixing within the population consists of two groups, children and adults. Children interact most frequently with other children close to their own age, while adults interact with a wider range of age groups and the durations of typical adult contacts are shorter than typical contacts between children. Furthermore, the transmission matrix shows that children are more likely to acquire infection than adults.     

Social workers, parents and stigma

This paper draws on an empirical study of stigma and child welfare services in the United Kingdom, the Netherlands, and Spain. It focuses exclusively on the findings relating to the United Kingdom and shows how stigma continues to be a part of the experience of using and delivering child welfare services, despite the positive determination of policies that this should not be so. More optimistically, however, it is also evident that the experience of stigma and exclusion can be reduced, and the paper concludes by outlining the implications for policy and practice together with those factors which would appear to be most significant in combating stigma.     

Testing the Significance of Categorical Predictor Variables in Nonparametric Regression Models

In this paper we propose a test for the significance of categorical predictors in nonparametric regression models. The test is fully data-driven and employs cross-validated smoothing parameter selection while the null distribution of the test is obtained via bootstrapping. The proposed approach allows applied researchers to test hypotheses concerning categorical variables in a fully nonparametric and robust framework, thereby deflecting potential criticism that a particular finding is driven by an arbitrary parametric specification. Simulations reveal that the test performs well, having significantly better power than a conventional frequency-based nonparametric test. The test is applied to determine whether OECD and non-OECD countries follow the same growth rate model or not. Our test suggests that OECD and non-OECD countries follow different growth rate models, while the tests based on a popular parametric specification and the conventional frequency-based nonparametric estimation method fail to detect any significant difference.     

Vocal determinants of first impressions of young children

Audiotapes of the voices of77 preschool children were prepared. Subjects listened to the tapes, and then provided their impressions of the competence, leadership, dominance, warmth, and honesty of the children. Judgments of the voices' babyishness and attractiveness were also obtained. Perceivers reliably discriminated the children's voices along the dimensions of babyishness and attractiveness. Moreover, analyses revealed that the previously documented impact of these characteristics on first impressions of adults extends to impressions of young children. The similarity of the effects of these characteristics on impressions formed about children to those revealed for adults suggests that vocal qualities may have an impact on personality development via a process of self-fulfilling prophecy.     

Developmental Career Counseling with Teenage Parents

Although teenage parenthood is recognized by many counselors as a developmental identity crisis, it rarely has been viewed as a developmental career crisis. This article suggests developmental career assessment and counseling procedures for use with teenage parents.