An EM Algorithm for Smoothing the Self-consistent Estimator of Survival Functions with Interval-censored Data

Interval-censored data arise in a wide variety of application and research areas such as, for example, AIDS studies (Kim et al ., 1993) and cancer research (Finkelstein, 1986; Becker & Melbye, 1991). Peto (1973) proposed a Newton–Raphson algorithm for obtaining a generalized maximum likelihood estimate (GMLE) of the survival function with interval-cen sored observations. Turnbull (1976) proposed a self-consistent algorithm for interval-censored data and obtained the same GMLE. Groeneboom & Wellner (1992) used the convex minorant algorithm for constructing an estimator of the survival function with "case 2" interval-censored data. However, as is known, the GMLE is not uniquely defined on the interval [0, ∞]. In addition, Turnbull's algorithm leads to a self-consistent equation which is not in the form of an integral equation. Large sample properties of the GMLE have not been previously examined because of, we believe, among other things, the lack of such an integral equation. In this paper, we present an EM algorithm for constructing a GMLE on [0, ∞]. The GMLE is expressed as a solution of an integral equation. More recently, with the help of this integral equation, Yu et al . (1997a, b) have shown that the GMLE is consistent and asymptotically normally distributed. An application of the proposed GMLE is presented     

Development and Consideration of Global Policies for Managing the Future Risks of Poliovirus Outbreaks: Insights and Lessons Learned Through Modeling

The success of the Global Polio Eradication Initiative promises to bring large benefits, including sustained improvements in quality of life (i.e., cases of paralytic disease and deaths avoided) and costs saved from cessation of vaccination. Obtaining and maintaining these benefits requires that policymakers manage the transition from the current massive use of oral poliovirus vaccine (OPV) to a world without OPV and free of the risks of potential future reintroductions of live polioviruses. This article describes the analytical journey that began in 2001 with a retrospective case study on polio risk management and led to development of dynamic integrated risk, economic, and decision analysis tools to inform global policies for managing the risks of polio. This analytical journey has provided several key insights and lessons learned that will be useful to future analysts involved in similar complex decision-making processes.     

Self-advocates have the last say on friendship

This study reports the friendship experiences and aspirations of adults with intellectual disabilities. The findings of a larger study were reviewed by an expert group of self-advocates with intellectual disability. The expert group confirmed some of the interpretation of the original data and expanded on issues. Friendship is established as an issue of concern among adults with intellectual disability. Consequently, policy-makers and service providers need to be intentional about providing support for friendships. Participants asserted a positive self-identity of being a person with intellectual disability and how this could be a basis for friendship. Also, people with intellectual disability demonstrated how they should be considered experts in their own life experience and how they can be effectively included in the formulation, implementation, analysis and review of research.     

Regularization and variable selection via the elastic net

Summary.  We propose the elastic net, a new regularization and variable selection method. Real world data and a simulation study show that the elastic net often outperforms the lasso, while enjoying a similar sparsity of representation. In addition, the elastic net encourages a grouping effect, where strongly correlated predictors tend to be in or out of the model together. The elastic net is particularly useful when the number of predictors ( p ) is much bigger than the number of observations ( n ). By contrast, the lasso is not a very satisfactory variable selection method in the p ≫ n case. An algorithm called LARS-EN is proposed for computing elastic net regularization paths efficiently, much like algorithm LARS does for the lasso.     

The photo‐survey research method: capturing life in the city

Recent promotion of city centre living within UK policy has led to a commensurate interest in city centre conditions and the opinions and experiences of the people who live there. An apposite, straightforward method to capture city centre residents' experiences and views is described in this article. We successfully combined a novel, under‐utilized visual technique (self‐directed photography) with qualitative methods (log‐sheets and interviews) in the form of a ‘photo‐survey’. A background to visual methodologies is presented in this article, alongside a critique of using the photo‐survey with 84 city centre residents to investigate environmental conditions and perceptions within three of the UK's major cities. The method provided a rich, detailed set of data, but also brought a number of noticeable benefits to the data collection process. The photo‐survey not only effectively captured and documented life in the city but also acted as an ‘agent for change’, evoking thoughts and feelings which ultimately encouraged participants to reflect on their existing perceptions and urban experiences. The study also raises some important considerations for future work undertaken with this method and with using photographs as a set of data, and proposes techniques for minimising potential problems.     

Relationship between body image and body mass index in college men

OBJECTIVE AND PARTICIPANTS: The authors examined cognitive and affective dimensions of body image of a randomized sample of 188 college men on the basis of body mass index (BMI). METHODS: They conducted chi-square tests and ANOVAs to determine differences between 4 BMI groups (underweight, normal weight, overweight, and obese) on demographics and body image measures. RESULTS: The authors found significant differences in regard to total body image (p < .001), weight or shape concern (p < .001), and body dissatisfaction (p < .001). BMI was significantly correlated with negative body image. Overweight and obese participants reported significantly higher levels of negative body image than did normal- and underweight participants. Overweight participants reported significantly higher weight and shape concerns than did underweight, normal-weight, and obese participants. In regard to body dissatisfaction, underweight, overweight, and obese participants reported significantly higher levels of body dissatisfaction than that reported by normal-weight participants. CONCLUSIONS: BMI may be an important factor in identifying potential body image disorders in college-aged men.     

Local and foreign models of reproduction in Nyanza Province, Kenya

This article uses colonial archival records, surveys conducted in the 1960s, and surveys and focus group discussions in the 1990s to describe three distinct but temporally overlapping cultural models of reproduction in a rural community in Kenya between the 1930s and the present. The first model, “large families are rich,” was slowly undermined by developments brought about by the integration of Kenya into the British empire. This provoked the collective formulation of a second local model, “small families are progressive,” which retained the same goal of wealth but viewed a smaller family as a better strategy for achieving it. The third model, introduced by the global networks of the international population movement in the 1960s, augmented the second model with the deliberate control of fertility using clinic provided methods of family planning. By the 1990s this global model had begun to be domesticated as local clinics routinely promoted family planning and as men and women in Nyanza began to use family planning and to tell others of their motivations and experiences.