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851.
Both treatment efficacy and safety are typically the primary endpoints in Phase II, and even in some Phase III, clinical trials. Efficacy is frequently measured by time to response, death, or some other milestone event and thus is a continuous, possibly censored, outcome. Safety, however, is frequently measured on a discrete scale; in Eastern Cooperative Oncology Group clinical trial E2290, it was measured as the number of weekly rounds of chemotherapy that were tolerable to colorectal cancer patients. For the joint analysis of efficacy and safety, we propose a non-parametric, computationally simple estimator for the bivariate survival function when one time-to-event is continuous, one is discrete, and both are subject to right-censoring. The bivariate censoring times may depend on each other, but they are assumed to be independent of both event times. We derive a closed-form covariance estimator for the survivor function which allows for inference to be based on any of several possible statistics of interest. In addition, we derive its covariance with respect to calendar time of analysis, allowing for its use in sequential studies. 相似文献
852.
Mediation and moderation are two theories for refining and understanding a causal relationship. Empirical investigation of
mediators and moderators requires an integrated research design rather than the data analyses driven approach often seen in
the literature. This paper described the conceptual foundation, research design, data analysis, as well as inferences involved
in a mediation and/or moderation investigation in both experimental and non-experimental (i.e., correlational) contexts. The
essential distinctions between the investigation of mediators and moderators were summarized and juxtaposed in an example
of a causal relationship between test difficulty and test anxiety. In addition, the more elaborate models, moderated mediation
and mediated moderation, the use of structural equation models, and the problems with model misspecification were discussed
conceptually.
相似文献
Bruno D. ZumboEmail: |
853.
Is the Study of Happiness a Worthy Scientific Pursuit? 总被引:1,自引:1,他引:0
This paper critiques the view that the study of happiness is not a worthy scientific pursuit. The happiness set point and
hedonic treadmill theories denote the complexity of increasing happiness levels due to genetic limitations and adaptation,
however, there is mounting evidence to suggest that with the use of appropriate measures and specific interventions aimed
at fostering strengths and virtues, happiness can be increased. Furthermore, the benefits of investigating methods for increasing
happiness include improvements in physical, psychological and social health and well-being. It is concluded that approaching
human needs from a top down or holistic standpoint where individuals can use their strengths to overcome life’s challenges,
is beneficial to health and well-being. Hence, the study of happiness is a worthy scientific pursuit. 相似文献
854.
This paper characterizes vulnerable workers in Canada and the federal jurisdiction, based upon characteristics such as employment
status, demographic characteristics, and job characteristics, and identifies areas in which labour standards may have a role.
Based on this analysis, the paper evaluates the potential for labour standards to address economic vulnerability, focusing
on labour standards policies aimed at wages and benefits, hours, and employment arrangements. In addition, the analysis considers
the extent to which labour standards are likely to reach vulnerable workers. The results suggest several potential roles for
labour standards and highlights policy implications.
相似文献
George A. SlotsveEmail: |
855.
856.
A single latent variable model of health status and therapeutic health care utilization is estimated for parents and own children
of 6,557 US households. The equation system that identifies latent health status simultaneously determines a number of indicators
of general health, including presence of morbidity symptoms, mobility limitations, medication needs, and utilization of therapeutic
health care services. The main goal of the paper was to obtain an unbiased estimate of parents’ marginal substitution rate
between own and child health. Results indicate that parents’ valuation of their children’s health exceeds their valuation
of own health by almost twofold on average.
相似文献
Thomas D. CrockerEmail: |
857.
This article uses a demographic approach and data from the Health and Retirement Survey, a nationally representative sample of the U.S. population, to investigate sex differences in the length of life lived with heart disease and after a heart attack for persons in the United States age 50 and older. On average, women live longer than men with heart disease. At age 50 women can expect to live 7.9 years and men 6.7 years with heart disease. The average woman experiences heart disease onset three years older and heart attacks 4.4 years older than men. 相似文献
858.
As STD infections including HIV increase in the United States, it has become increasingly important to policy makers to ascertain the extent to which knowledge and perceptions of AIDS risk affect an individual's probability of altering their sexual or contraceptive behavior to avoid infection. This paper examines the extent to which women's perceptions of their own and their partners' risk of HIV infection affects the probability of using a condom for protection against sexually transmitted diseases. This paper also examines the extent to which HIV testing may affect motivation for condom use. Crosstabulations reveal that prophylactic condom use is more prevalent among women who have been tested for HIV and increase as perceptions of their chance (and their partner's chance) of being positive increases. The multivariate results from this study indicate that having an HIV test significantly predicts the likelihood of using a condom for STD prevention for US women. Furthermore, women who perceive themselves to be at least somewhat likely to be HIV positive have a higher probability of using a condom to prevent sexually transmitted disease, and women who perceive their partners to be HIV positive are twice as likely as other women to use a condom for STD prevention. However, women who consider themselves likely to be HIV positive are no more likely to use a condom than those who consider themselves not at risk. 相似文献
859.
Scientific techniques for inventory management typically are applied to systems containing many items. Such techniques require an estimation of the demand variance (and mean) of each item from historical data. This research demonstrates a significant potential for improvement in system cost performance from using least-squares regression fits of a variance-to-mean functional relation instead of the standard statistical variance estimate. Even when there is a moderate degree of heterogeneity among items and when the form of the variance-to-mean relation is misspecified, substantial cost savings may be realized. The cost of statistical uncertainty may be reduced by half. The research also provides evidence that system cost is fairly insensitive to the number of items used to fit the regression. This paper provides the underlying reason why a regression-derived variance estimator yields lower cost: it is less variable than the usual individual item variance estimator. 相似文献
860.
Philip A. Cowan Carolyn Pape Cowan Marsha Kline Pruett Kyle Pruett Jessie J. Wong 《Journal of marriage and the family》2009,71(3):663-679
Few programs to enhance fathers' engagement with children have been systematically evaluated, especially for low‐income minority populations. In this study, 289 couples from primarily low‐income Mexican American and European American families were randomly assigned to one of three conditions and followed for 18 months: 16‐week groups for fathers, 16‐week groups for couples, or a 1‐time informational meeting. Compared with families in the low‐dose comparison condition, intervention families showed positive effects on fathers' engagement with their children, couple relationship quality, and children's problem behaviors. Participants in couples' groups showed more consistent, longer term positive effects than those in fathers‐only groups. Intervention effects were similar across family structures, income levels, and ethnicities. Implications of the results for current family policy debates are discussed. 相似文献