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1.
Proportional hazards are a common assumption when designing confirmatory clinical trials in oncology. This assumption not only affects the analysis part but also the sample size calculation. The presence of delayed effects causes a change in the hazard ratio while the trial is ongoing since at the beginning we do not observe any difference between treatment arms, and after some unknown time point, the differences between treatment arms will start to appear. Hence, the proportional hazards assumption no longer holds, and both sample size calculation and analysis methods to be used should be reconsidered. The weighted log‐rank test allows a weighting for early, middle, and late differences through the Fleming and Harrington class of weights and is proven to be more efficient when the proportional hazards assumption does not hold. The Fleming and Harrington class of weights, along with the estimated delay, can be incorporated into the sample size calculation in order to maintain the desired power once the treatment arm differences start to appear. In this article, we explore the impact of delayed effects in group sequential and adaptive group sequential designs and make an empirical evaluation in terms of power and type‐I error rate of the of the weighted log‐rank test in a simulated scenario with fixed values of the Fleming and Harrington class of weights. We also give some practical recommendations regarding which methodology should be used in the presence of delayed effects depending on certain characteristics of the trial. 相似文献
2.
Alison Snow Jones 《Journal of Family and Economic Issues》2002,23(1):3-25
The association between drinking and selected job characteristics among women aged 24 to 31 is examined. Using the 1989 NLSY, women are classified as alcohol abusers or dependent based on DSM-III-R criteria or as heavy drinkers based on reported frequency of six or more drinks. Heavy drinking is negatively associated with wage and non-wage compensation. These effects diminish when human capital measures are controlled. Current alcoholism and current and past heavy drinking are strongly negatively associated with years of schooling. The association between alcoholism and job compensation and characteristics is not as strong as that seen for heavy drinking. It is not known if this is a consequence of errors in identifying alcoholic women in population-based surveys. 相似文献
3.
A NOTE ON EVANESCENT PROCESSES 总被引:1,自引:0,他引:1
This note examines the connection between μ-invariant measures for the transition function of a continuous-time Markov chain and those of its q-matrix, Q. The major result establishes a necessary and aufficient condition for a convergent μ-invariant measure for Q to be μ-inhant for the minimal transition function, P, under the assumption that P is honest. This corrects Theorem 6 of Vere-Jones (1969) and the first part of Corollary 1 of Pollett (1986), both of which assert that the above conclusion holds in the absence of this condition. The error was pointed out by E.A. van Doom (1991) and the counterexample which be presented provides the basis for the present arguments. In determining where the error occurred in the original proof, we are able to identify a simple sufficient condition for μ-invariance. 相似文献
4.
Chris Jones 《Significance》2008,5(1):46-48
It rises massive and magnificent above Salisbury Plain. The extraordinary monoliths of Stonehenge leave us as impressed today as ever—and as baffled. Archaeologists argue about how it was made. Can statisticians tell the answer? Chris Jones thinks they can be of considerable assistance. 相似文献
5.
Rachel K. Jones 《Sociological inquiry》1993,63(3):351-361
Victims of spouse abuse were interviewed concerning their views of why their husbands were abusive. It was hypothesized that by concentrating on one specific characteristic of this kind previously undocumented patterns of response would be elicited from the subjects. It was concluded that the women's reasons for the violence perpetrated by their spouses serve as justification for the abusers’actions and legitimize maintenance of the relationship. 相似文献
6.
Melissa S. Waters R. Carter Hill William J. Moore Robert J. Newman 《Journal of Labor Research》1994,15(4):355-372
This paper estimates a simultaneous-equations model with public sector bargaining laws and union membership treated as jointly-determined
variables. The extent of public sector unionization has a significant positive influence on the passage of prolabor bargaining
legislation and bargaining legislation has strong, independent effects on the extent of public sector unionization.
We gratefully acknowledge the research support provided by Minbo Kim and Parisun Chantonahom. 相似文献
7.
How do new parents differ from their childless counterparts in social and psychological resources, daily strains, and psychological well‐being? Using a nationally representative panel of 1,933 adults who were childless at the first interview, we compare 6 indicators of adults' lives for those who became parents and those remaining childless several years later, controlling for earlier states. Becoming a parent is both detrimental and rewarding. With the exception of social integration, which is greater for all groups of new parents compared with their childless counterparts, the effects of parental status on adults' lives vary markedly by gender and marital status. Unmarried parents report lower self‐efficacy and higher depression than their childless counterparts. Married mothers' lives are marked by more housework and more marital conflict but less depression than their childless counterparts. Parental status has little influence on the lives of married men. 相似文献
8.
Chandan Saha Michael P. Jones 《Journal of the Royal Statistical Society. Series B, Statistical methodology》2005,67(1):167-182
Summary. In longitudinal studies, missingness of data is often an unavoidable problem. Estimators from the linear mixed effects model assume that missing data are missing at random. However, estimators are biased when this assumption is not met. In the paper, theoretical results for the asymptotic bias are established under non-ignorable drop-out, drop-in and other missing data patterns. The asymptotic bias is large when the drop-out subjects have only one or no observation, especially for slope-related parameters of the linear mixed effects model. In the drop-in case, intercept-related parameter estimators show substantial asymptotic bias when subjects enter late in the study. Eight other missing data patterns are considered and these produce asymptotic biases of a variety of magnitudes. 相似文献
9.
Melissa S. Herbert Ph.D. candidate in Sociology 《Gender Issues》1994,14(2):25-48
Attitudes toward the role of women in the military require the reconciliation of two often conflicting beliefs: those toward
the roles and rights of women and those toward the military. This article explores the relationships between positive attitudes
toward women’s roles throughout society, or feminism, and positive attitudes toward defense spending, or militarism, both
with each other and with attitudes toward gender integration in the military. Results of this analysis show there to be a
negative relationship between feminism and militarism, a positive relationship between feminism and gender integration, and
a negative relationship between militarism and gender integration. The results of multiple regression analysis show that feminism
is the strongest predictor of attitudes toward gender integration, while militarism is weak in its predictive ability. The
author argues that the issue of women in the military is more one of women’s equality than of national defense and that policy
discussions should be structured accordingly.
She is currently conducting research which examines how women in the United States military employ strategies to manage gender
and sexuality. This research provides evidence for the claim that gender is not simply a role or an attribute, but that gender
is created and recreated through our interactions with others. 相似文献
10.
Rex Forehand Deborah J. Jones Gene H. Brody Lisa Armistead 《Journal of marriage and the family》2002,64(4):1012-1023
This study examined the unique and interactive roles of mother and teacher depressive symptoms in child adjustment in 277 African American single mother‐headed families, as well as whether the associations differed depending on the age and gender of the child. Findings revealed a significant association between maternal depressive symptoms and child depressive symptoms in girls, but not boys. Moreover, the combination of higher levels of both mother and teacher depressive symptoms was associated with the highest level of child depressive symptoms and, for younger children, externalizing symptoms. The importance of considering the multiple social contexts in which children interact is discussed. 相似文献