Motivated by a breast cancer research program, this paper is concerned with the joint survivor function of multiple event times when their observations are subject to informative censoring caused by a terminating event. We formulate the correlation of the multiple event times together with the time to the terminating event by an Archimedean copula to account for the informative censoring. Adapting the widely used two-stage procedure under a copula model, we propose an easy-to-implement pseudo-likelihood based procedure for estimating the model parameters. The approach yields a new estimator for the marginal distribution of a single event time with semicompeting-risks data. We conduct both asymptotics and simulation studies to examine the proposed approach in consistency, efficiency, and robustness. Data from the breast cancer program are employed to illustrate this research.
VII. Conclusion The number of immigrants now coming to the United States is proportionally only a fraction of the number that came in earlier
years, and there is nothing in those numbers to suggest a difficult absorption burden. Immigrants, both legal and illegal,
more than pay for the services they use with the taxes they pay, leaving a considerable net surplus that benefits American
citizens. Immigrants raise productivity and do not cause an observable amount of unemployment of citizens. Admitting far more
immigrants into the country than the law now allows would have positive effects on the incomes of citizens, and would enhance
the continuing vitality of the United States. 相似文献
This article presents the findings of a small scale qualitative study of user perspectives in the adolescent sexual aggression field. Twenty four service users who had received intervention from nine different specialist providers completed a structured questionnaire about their experiences of professional involvement. Both young people who had sexually abused and parents identified the kinds of professional intervention which they found useful, as well as practices that they experienced as unhelpful. Young people and their families alike were found to value supportive interventions which gave them an opportunity to gain insight into the nature of sexual abuse as well to address their own feelings about their problems. 相似文献
The new FT House Price Index aims to end the confusion that arises from the current plethora of indices. Simon Briscoe examines these various indices and explains the methodology behind the FT Index. 相似文献
As new technologies, video-games are becoming increasingly popular among today's pre-teens and teenagers. Relying on systematic observation of videogames found in public arcades, participation in them, and engagement with the relevant literature, I explore eight central assumptions of “videology”: the ideology which organizes these games. While suggesting that these assumptions articulate and exaggerate problematic ideological themes, I also explore the relationship between videology and a postmodern culture or moment. 相似文献
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. 相似文献