What to Do at Low Doses: A Bounding Approach for Economic Analysis

To quantify the health benefits of environmental policies, economists generally require estimates of the reduced probability of illness or death. For policies that reduce exposure to carcinogenic substances, these estimates traditionally have been obtained through the linear extrapolation of experimental dose-response data to low-exposure scenarios as described in the U.S. Environmental Protection Agency's Guidelines for Carcinogen Risk Assessment (1986). In response to evolving scientific knowledge, EPA proposed revisions to the guidelines in 1996. Under the proposed revisions, dose-response relationships would not be estimated for carcinogens thought to exhibit nonlinear modes of action. Such a change in cancer-risk assessment methods and outputs will likely have serious consequences for how benefit-cost analyses of policies aimed at reducing cancer risks are conducted. Any tendency for reduced quantification of effects in environmental risk assessments, such as those contemplated in the revisions to EPA's cancer-risk assessment guidelines, impedes the ability of economic analysts to respond to increasing calls for benefit-cost analysis. This article examines the implications for benefit-cost analysis of carcinogenic exposures of the proposed changes to the 1986 Guidelines and proposes an approach for bounding dose-response relationships when no biologically based models are available. In spite of the more limited quantitative information provided in a carcinogen risk assessment under the proposed revisions to the guidelines, we argue that reasonable bounds on dose-response relationships can be estimated for low-level exposures to nonlinear carcinogens. This approach yields estimates of reduced illness for use in a benefit-cost analysis while incorporating evidence of nonlinearities in the dose-response relationship. As an illustration, the bounding approach is applied to the case of chloroform exposure.     

A LOTTO SYSTEMS PROBLEM

A Lotto Systems bet allows the player to nominate n numbers from which (s)he believes the winning six numbers will be drawn, and to bet on all combinations of six of these n numbers. Assume that the winning six numbers come from the nominated n. How many combinations must be entered to guarantee that one combination will include at least five of the winning six numbers? The problem is generalized in this paper, and the method of simulated annealing is used to find solutions for various situations. The case where two supplementary numbers are drawn after the initial six winning numbers is also considered.     

Children's involvement in their parents' divorce: implications for practice

The paper reports findings from a research study that explored children's experience of divorce. It shows that children experience parental divorce as a crisis in their lives but that they are able to mobilise internal and external resources to regain a new point of balance. In doing so, children demonstrate the degree to which they are active and competent participants in the process of family dissolution. The implications of the data are then considered in relation to engaging with children involved in divorce and in relation to some of the cultural presumptions that might militate against hearing what they have to say about their experiences. Copyright © 2002 John Wiley & Sons, Ltd.     

Real Men,Real Women,Real Lives? Gender issues in learning disabilities and challenging behaviour

This article seeks to define gender issues and explores the significance of these issues for challenging behaviour in the field of learning disability. It is argued that lack of awareness about these issues contributes to the development of challenging behaviour and to difficulties in identifying the needs expressed through these behaviours, whatever their origin. Specific areas examined include models of residential provision for adults, prioritisation of service activities, attribution processes (needs identification), and the sexuality of people with learning disabilities. In each area issues are raised and the implications for service practice defined.     

An exploratory study of gambling cross addictions

A growing body of empirical and theoretical research has concentrated on the overlaps and commonalities among chemical and non-chemical (behavioural) addictions. Pathological gambling has perhaps been the most widely researched behavioural addiction and some of this research has concerned the co-existing links between pathological gambling and alcohol/drug addiction in both the gambling substance abuser and the substance abusing gambler (i.e. cross addiction). This study was of an exploratory nature and attempted to gather information and data regarding gambling cross addictions in the UK. To achieve this, 456 letters were sent to all drug and alcohol helping agencies in England requesting such information. This yielded 210 returns (46% response rate). Results indicated that gambling cross addictions occur in both adults and adolescents and were almost exclusively a male condition. However, it must be noted only just over half of the responding agencies had encountered gambling cross addiction and reasons for this are speculated. Results also indicated the existence of various cross addicted subgroups including an adolescent subgroup who were addicted to fruit machines and abused solvents. Future research ideas are also discussed.A more detailed version of this paper is available from the author on request.     

Issues in applying recent CPMP ‘Points to Consider’ and FDA guidance documents with biostatistical implications

The International Conference on Harmonisation guideline ‘Statistical Principles for Clinical Trials’ was adopted by the Committee for Proprietary Medicinal Products (CPMP) in March 1998, and consequently is operational in Europe. Since then more detailed guidance on selected topics has been issued by the CPMP in the form of ‘Points to Consider’ documents. The intent of these was to give guidance particularly to non‐statistical reviewers within regulatory authorities, although of course they also provide a good source of information for pharmaceutical industry statisticians. In addition, the Food and Drug Administration has recently issued a draft guideline on data monitoring committees. In November 2002 a one‐day discussion forum was held in London by Statisticians in the Pharmaceutical Industry (PSI). The aim of the meeting was to discuss how statisticians were responding to some of the issues covered in these new guidelines, and to document consensus views where they existed. The forum was attended by industry, academic and regulatory statisticians. This paper outlines the questions raised, resulting discussions and consensus views reached. It is clear from the guidelines and discussions at the workshop that the statistical analysis strategy must be planned during the design phase of a clinical trial and carefully documented. Once the study is complete the analysis strategy should be thoughtfully executed and the findings reported. Copyright © 2003 John Wiley & Sons, Ltd.     

The star-shaped Λ-coalescent and Fleming–Viot process

The star-shaped Λ-coalescent and corresponding Λ-Fleming–Viot process, where the Λ measure has a single atom at unity, are studied in this article. The transition functions and stationary distribution of the Λ-Fleming–Viot process are derived in a two-type model with mutation. The distribution of the number of non-mutant lines back in time in the star-shaped Λ-coalescent is found. Extensions are made to a model with d types, either with parent-independent mutation or general Markov mutation, and an infinitely-many-types model, when d → ∞. An eigenfunction expansion for the transition functions is found, which has polynomial right eigenfunctions and left eigenfunctions described by hyperfunctions. A further star-shaped model with general frequency-dependent change is considered and the stationary distribution in the Fleming–Viot process derived. This model includes a star-shaped Λ-Fleming–Viot process with mutation and selection. In a general Λ-coalescent explicit formulae for the transition functions and stationary distribution, when there is mutation, are unknown. However, in this article, explicit formulae are derived in the star-shaped coalescent.     

Measuring Children's Experience of Their Right to Participate in School and Community: A Rights‐Based Approach

This paper discusses the development of a children's rights‐based measure of participation and the findings from its use in a survey of 10‐ to 11‐year‐old children (n = 3773). The measure, which was developed in collaboration with a group of children, had a high reliability (Cronbach's alpha = 0.89). Findings suggest that children's positive experience of their participation rights is higher in school than in community, and higher for girls compared to boys. It is argued that involving children in the ‘measurement’ of their own lives has the potential to generate more authentic data on children's lived experiences.     

Factors That Impact a Social Worker's Capacity to Supervise a Student

With sector constraints and higher education economic imperatives increasingly impacting the provision of social work field education, university programs lack an understanding of the factors that enable or prohibit field educators’ capacity to provide placements. Despite the significance of field education in the curriculum, it remains unclear what the experiences and motivations of field educators are to provide universities with student placements. This research addresses this gap through surveying 101 field educators that attended statewide Victorian field education training. Results indicated that although field educators recognised the benefits of supervising students, workload relief, additional training, and further student placement preparation by the university were emphasised as the primary factors that would enable them to respond positively to placement requests. Payments for placements did not necessarily ameliorate these issues nor guarantee the provision of more placements. The implications of these findings for universities and the field are discussed.