Optimal composite scores for longitudinal clinical trials under the linear mixed effects model

Clinical trials of chronic, progressive conditions use rate of change on continuous measures as the primary outcome measure, with slowing of progression on the measure as evidence of clinical efficacy. For clinical trials with a single prespecified primary endpoint, it is important to choose an endpoint with the best signal‐to‐noise properties to optimize statistical power to detect a treatment effect. Composite endpoints composed of a linear weighted average of candidate outcome measures have also been proposed. Composites constructed as simple sums or averages of component tests, as well as composites constructed using weights derived from more sophisticated approaches, can be suboptimal, in some cases performing worse than individual outcome measures. We extend recent research on the construction of efficient linearly weighted composites by establishing the often overlooked connection between trial design and composite performance under linear mixed effects model assumptions and derive a formula for calculating composites that are optimal for longitudinal clinical trials of known, arbitrary design. Using data from a completed trial, we provide example calculations showing that the optimally weighted linear combination of scales can improve the efficiency of trials by almost 20% compared with the most efficient of the individual component scales. Additional simulations and analytical results demonstrate the potential losses in efficiency that can result from alternative published approaches to composite construction and explore the impact of weight estimation on composite performance. Copyright © 2016. The Authors. Pharmaceutical Statistics Published by John Wiley & Sons Ltd.     

Une typologie des économies selon les dimensions de l'emploi dans l'économie informelle

Compte tenu de l'importance des activités informelles, l'auteur propose de classer les pays selon les dimensions de l'emploi dans l'économie informelle plutôt que selon la composition de l'économie formelle. A partir de données du BIT portant sur trente‐six pays en développement, il fait apparaître une corrélation significative entre l'étendue et l'intensité de l'informalité et différents indicateurs sociaux et économiques: PNB par habitant, degré de corruption et de pauvreté et niveau de l'impôt et des cotisations sociales. Les implications de ces résultats pour la réflexion théorique et l'action sont ensuite exposées.     

An experimental test of several generalized utility theories

There is much evidence that people willingly violate expected utility theory when making choices. Several axiomatic theories have been proposed to explain some of this evidence, but there are few data that discriminate between the theories. To gather such data, an experiment was conducted using pairs of gambles with three levels of outcomes and many combinations of probabilities. Most typical findings were replicated, including the common consequence effect and different risk attitudes for gains and losses. There is evidence of both fanning out and fanning in of indifference curves, and both quasiconcavity and quasiconvexity of preferences. No theory can explain all the data, but prospect theory and the hypothesis that indifference curves fan out can explain most of them.The Wharton School,University of Pennsylvania     

WHO BUYS HEALTH INSURANCE? A SURVEY OF TWO LARGE ORGANISATIONS

Despite the importance of private insurance in the financing of Australia's health care system, there have been few studies of health insurance choice. A survey was carried out of employees of two large organisations to serve as a reference group for middle-income people in secure employment. Insurance was associated with income, age, marital status and history of medical costs; but not dependents or hospital expenses. Main determinants of level of cover were income and medical costs. In making decisions, information search was low and decisions seem to be made on the basis of simple risk aversion, influenced by insurers' advertising.     

Combining Measures of Risk Perceptions and Risk Activities: The Development of the RAPRA and PRISC Indices

The influence of risk perceptions on risk activities of teenagers is well known, but the development of indices, which combine measures of perception as well as behavioral outcomes, has proved problematical. This article discusses the ways in which this methodological problem was tackled within a five-year, multiphase, multimethod study of factors affecting adolescent risk-taking in Tasmania, Australia, which included an intergenerational comparison of adolescents and parents. The development of the Risk Activity by Personal Risk Assessment (RAPRA) Index combines measures of perceived riskiness of 26 activities identified by young people as involving varying degrees of risk, with the degree of participation by each respondent, through a rectangular model of weights. The Personal Risk Score Category (PRISC) Index summarizes and categorizes an individual's risk-taking profile relative to the group's risk values and risk hierarchy established by the RAPRA Index. The article discusses ways in which technical problems involved in combining measures of risk perceptions and risk activities were addressed during index construction, compared with examples in the literature. Some key findings from analysis of two student and parent samples are presented as exemplars of the methods used and the results produced. Findings demonstrate the widespread nature of risk-taking among teenagers, and the similarity of levels of risk-taking between teenager and parental generations. The indices allow for detailed comparison of particular risk-taking activities and reveal differences among teenagers now compared with parents when they were teenagers, and illustrate the dynamic cultural context of risk-taking perceptions and values.     

The 'family wage' as a class-rational strategy

This paper re-examines the debate about the class rationality of the working-class demand for a family wage and argues that this issue cannot be resolved without considering the feasibility of alternative strategies. Existing accounts are criticized for their unrealistic treatment of these alternatives and the constraints upon them and particularly for their neglect of the influence of the policies of employers and the state upon working-class strategies. The argument is supported by discussion of the economic and political context of the family wage demand in Britain up to the First World War and concludes that the strategy was more rational than many writers have suggested.     

Reviewing child deaths—learning from the American experience

Current systems for investigating child deaths in England, Wales and Northern Ireland have come under intense scrutiny in recent years and questions have been raised about the accuracy of child death investigations and resulting statistics. Research has highlighted the ways in which multidisciplinary input can contribute to investigative and review processes, a perspective which is further supported by recent UK policy developments. The experience of creating multidisciplinary child death review teams (CDRTs) in America highlights the potential benefits the introduction of a similar system might have. These benefits include improved multi‐agency working and communication, more effective identification of suspicious cases, a decrease in inadequate death certification and a broader and more in‐depth understanding of the causes of child deaths through the systematic collection and analysis of data. While a lack of funding, regional coordination and evaluation limit the impact of American CDRTs, the positive aspects of this process make it worthwhile, and timely, to consider how such a model might fit within our own context. Current policy developments such as the Home Office review of coroner services, the Children Bill and related Department for Education and Skills (DfES) work on developing screening groups demonstrate that strides have been made in respect of introducing a multidisciplinary process. Similarly, the development of local protocols for the investigation and[sol ]or review of child deaths in England, Wales and Northern Ireland highlights an increased focus on multidisciplinary processes. However, key issues from the American experience, such as the remit of CDRTs[sol ]screening panels, the need for national coordination and the importance of rigorous evaluation, can inform the development of a similar process in the UK. Copyright © 2005 John Wiley & Sons, Ltd.