TESTING FOR CONTINUOUS LOCAL MARTINGALES USING THE CROSSING TREE

We present statistical tests for the continuous martingale hypothesis; that is, for whether an observed process is a continuous local martingale, or equivalently a continuous time‐changed Brownian motion. Our technique is based on the concept of the crossing tree. Simulation experiments are used to assess the power of the tests, which is generally higher than that of recently proposed tests using the estimated quadratic variation (i.e. realized volatility). In particular, the crossing tree shows significantly higher power with shorter data sets. We then show results from applying the methodology to five high‐frequency currency exchange rate data sets from 2003. For four of them we show that at small time‐scales (less than 15 minutes or so) the continuous martingale hypothesis is rejected, but not so at larger time‐scales. For the fifth, the hypothesis is rejected at small time‐scales and at some moderate time‐scales, but not all.     

From passive to active consumers? Later life consumption in the UK from 1968–2005

The significance of the UK's ageing population has been generally acknowledged, however its implications for consumption have been neglected. The consumption patterns of older people are important given that the end of the 20^th century witnessed profound changes to the nature of later life, many linked to the emergence of 'consumer societies' in the UK and elsewhere. The uneven nature of retirement, as well as the relative affluence of many retired people, has important effects on patterns and experiences of consumption. This paper charts consumption by retired households in two areas; ownership of key consumer goods and key components of household spending. We investigate how these expenditure trends compare with other household types and across pseudo-birth cohorts. We draw data from 9 years of the Family Expenditure Survey taken at 5 year intervals between 1968 and 2004/5. The data demonstrate the growing extent of ownership of key goods in retired households but also show the differences in proportional expenditure between retired households and the employed. We also note differences between pseudo-birth cohorts and conclude that consumption patterns in later life are influenced by the generational habitus of the differing cohorts who entered retirement between the 1960s and the present day.     

Living Arrangements,Knowledge of Health Risks,and Stress as Determinants of Health-Risk Behavior Among College Students

Abstract

The association of knowledge of health risks, living arrangements, and perceived stress with health-risk behaviors was examined in a sample of college students included in the Health Promotion and Disease Prevention Supplement of the National Health Interview Survey. Regressions of each health-risk behavior (dependent variable) were performed on the predicted correlates. Although knowledge was not associated with participation in physical activity or smoking, the study found that students who knew more about the harmful effects of alcohol drank less, and those with greater knowledge of health risks practiced fewer risky behaviors. Students living independently were more likely to smoke, and those living in residence halls were less like to do so. Drinking, however, was more common among students living in residence halls or independently than among those living at home. Hall residents engaged in more group physical activity than other students did, but their physical activity was unrelated to health-risk behaviors. Stress was associated with smoking but not with other health practices. The findings suggest that smoking may be less influenced by health knowledge and more associated than drinking is with a response to stress. Drinking appears to be a social activity associated with living among peers and is potentially modifiable by increased knowledge about the effects of alcohol on health.     

Research Subjects with Limited English Proficiency: Ethical and Legal Issues

In this article, we examine Institutional Review Board (IRB) policies, international guidelines, and federal regulations and guidance for dealing with Limited English Proficiency (LEP) research subjects. We show that federal and international guidance concerning this topic is insufficient, and there is considerable variation in IRB policies. While some IRBs have thorough and useful policies, others do not. Many IRBs do not provide researchers and IRB members with answers to several important questions relating to language barriers in research. We recommend that federal agencies, international organizations, IRBs, and researchers take steps to fill in the gaps in guidance and policy to help insure that LEP populations will receive equitable and ethical treatment in research.     

Selecting Nonpharmaceutical Interventions for Influenza

Models of influenza transmission have focused on the ability of vaccination, antiviral therapy, and social distancing strategies to mitigate epidemics. Influenza transmission, however, may also be interrupted by hygiene interventions such as frequent hand washing and wearing masks or respirators. We apply a model of influenza disease transmission that incorporates hygiene and social distancing interventions. The model describes population mixing as a Poisson process, and the probability of infection upon contact between an infectious and susceptible person is parameterized by p. While social distancing interventions modify contact rates in the population, hygiene interventions modify p. Public health decision making involves tradeoffs, and we introduce an objective function that considers the direct costs of interventions and new infections to determine the optimum intervention type (social distancing versus hygiene intervention) and population compliance for epidemic mitigation. Significant simplifications have been made in these models. However, we demonstrate that the method is feasible, provides plausible results, and is sensitive to the selection of model parameters. Specifically, we show that the optimum combination of nonpharmaceutical interventions depends upon the probability of infection, intervention compliance, and duration of infectiousness. Means by which realism can be increased in the method are discussed.     

Research subjects with limited English proficiency: ethical and legal issues

In this article, we examine Institutional Review Board (IRB) policies, international guidelines, and federal regulations and guidance for dealing with Limited English Proficiency (LEP) research subjects. We show that federal and international guidance concerning this topic is insufficient, and there is considerable variation in IRB policies. While some IRBs have thorough and useful policies, others do not. Many IRBs do not provide researchers and IRB member with answers to several important questions relating to language barriers in research. We recommend that federal agencies, international organizations, IRBs, and researchers take steps to fill in the gaps in guidance and policy to help insure that LEP populations will receive equitable and ethical treatment in research.