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241.
Starting from an applied Bone Marrow Transplantation(BMT) study, the problem of “unexpected protectivity” in competing risks
models is introduced, which occurs when one covariate shows a protective impact not expected from a medical perspective. Current
explanations found in the statistical literature suggest that unexpected protectivity might be due to the lack of independence
between the competing failures. Actually, in the presence of dependence, the Kaplan-Meier curves are not interpretable. Conversely,
the cumulative incidence curves remain interpretable, and therefore seem to be a candidate for solving the problem. We discuss
the particular nature of dependence in a competing risks framework and illustrate how this dependence may be created via a
common frailty factor. A Monte Carlo experiment is set up which accounts also for the association between the observable covariates
and the frailty factor. The aim of the experiment is to understand whether and how the bias showed by the estimates could
be related to the omitted frailty variable. The results show that dependence alone does not cause false protectivity, and
that the cumulative incidence curves suffer the same bias as the survival curves and therefore do not seem to be a solution
to false protectivity. Conversely, false protectivity may occur according to the magnitude and the sign of the dependence
between the frailty factor and the covariate. The paper ends with some suggestions for empirical research.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
242.
243.
Lourdes M. Rivera Eric C. Chen Lisa Y. Flores Fran Blumberg Joseph G. Ponterotto 《The Career development quarterly》2007,56(1):47-61
This study used path analysis to examine the relationship between perceived barriers, acculturation, and role model influence on the career self‐efficacy and career considerations of a sample of Hispanic women. Two path models were examined. The male‐dominated model accounted for 15% of the variance, and the female‐dominated model accounted for 26% of the variance. No relationship was found between the variables of interest and male‐dominated career self‐efficacy and consideration. However, perceived barriers were related to female‐dominated career consideration and Anglo acculturation significantly contributed to female‐dominated career self‐efficacy. Results are discussed with regard to career practice and research with Hispanic women. 相似文献
244.
Nafion溶液在燃料电池、电极修饰、电化学分析、电化学催化等领域具有广泛用途。采用特种高沸点溶剂,获得了溶铸性能优良Nafion的溶液。比较溶铸Nafion膜与原始Nafion膜的IR光谱可以看出,Nafion溶液制备方法未对Nafion膜的化学组成与分子结构产生影响,但溶铸膜的分子排列更加规整有序。将该溶液在PEMFC中应用,其性能优于目前的商品水-醇体系Nafion溶液。 相似文献
245.
LOFT原指阁楼、顶层楼,现在借指由废弃厂房改造而成的艺术家工作室。通过扼要介绍LOFT的概念、LOFT文化的发展,并以北京大山子艺术区的形成发展为例,着重分析了在个案改造中艺术家充分运用先锋时尚的艺术手段创造出特有的空间形象及文化品质过程,希望为LOFT文化的发展提供借鉴。 相似文献
246.
Joseph D. Reid 《Journal of Labor Research》1991,12(4):368-372
247.
The authors propose methods for Bayesian inference for generalized linear models with missing covariate data. They specify a parametric distribution for the covariates that is written as a sequence of one‐dimensional conditional distributions. They propose an informative class of joint prior distributions for the regression coefficients and the parameters arising from the covariate distributions. They examine the properties of the proposed prior and resulting posterior distributions. They also present a Bayesian criterion for comparing various models, and a calibration is derived for it. A detailed simulation is conducted and two real data sets are examined to demonstrate the methodology. 相似文献
248.
249.
嘉陵江洪化元年洪水问题 总被引:1,自引:0,他引:1
吴敌 《西华师范大学学报(自然科学版)》2002,(1):7-11
在四川长江干流及其支流嘉陵江流域曾发现多处“洪化元年洪水”岩刻,有学者据此认定该年嘉陵江流域发生过特大洪水。此文以为,洪化元年应为1679年,即康熙十八年,该年嘉陵江流域没有发生过特大洪水。 相似文献
250.
In this article a general result is derived that, along with a functional central limit theorem for a sequence of statistics, can be employed in developing a nonparametric repeated significance test with adaptive target sample size. This method is used in deriving a repeated significance test with adaptive target sample size for the shift model. The repeated significance test is based on a functional central limit theorem for a sequence of partial sums of truncated observations. Based on numerical results presented in this article one can conclude that this nonparametric sequential test performs quite well. 相似文献