Uniqueness of permuted treatment estimator distributions in the proportional hazards model

We discuss findings regarding the permutation distributions of treatment effect estimators in the proportional hazards model. For fixed sample size n, we will prove that all uncensored and untied event times yield the same permutation distribution of treatment effect estimators in the proportional hazards model. In other words this distribution is irrelevant with respect to the actual event times. We will show several uniqueness properties under different conditions. These properties are useful for small sample permutation tests and also helpful to large sample cases.     

Commentary: what role for the family and Medical Leave Act in long-term care policy?

The Family and Medical Leave Act provides unpaid leave but a key component is its intergenerational structure, permitting employees to take time off from work to care for an infant as well as an ill elderly parent. However, in an effort to provide paid leave, 23 of 28 states dropped the elder care provision in new initiatives introduced between 2000 and 2003. This article argues that in reforming leave policy in the future, the leave should be paid, remain intergenerational, cover more workers, and be adaptable to changing family patterns in an aging society. Also discussed is California's paid leave law, which meets these criteria.     

Health selection and the process of social stratification: the effect of childhood health on socioeconomic attainment

This study investigates whether childhood health acts as a mechanism through which socioeconomic status is transferred across generations. The study uses data from the Panel Study of Income Dynamics to track siblings and to estimate fixed-effects models that account for unobserved heterogeneity at the family level. The results demonstrate that disadvantaged social background is associated with poor childhood health. Subsequently, poor health in childhood has significant, direct, and large adverse effects on educational attainment and wealth accumulation. In addition, childhood health appears to have indirect effects on occupational standing, earnings, and wealth via educational attainment and adult health status. The results further show that socioeconomic health gradients are best understood as being embedded within larger processes of social stratification.     

Gay, lesbian, and bisexual foster parents: strengths and challenges for the child welfare system

Historically, a shortage of skilled and dedicated foster parents has existed in America. Lesbian, gay, or bisexual (LBG) foster parents have received little attention in the published literature. This article documents the challenges and successes of a group of 60 LGB foster parents. All participants provided foster parenting for public (state or county) agencies. The primary successes of this group included meaningful and gratifying parenting and successful testing of whether adoption might be a natural next step after foster parenting. The primary challenges included insensitive, inappropriate, and difficult social workers; state or local laws that worked against successful foster parenting by LGB adults; failure to recognize parents' partners; and lack of support by the system to acknowledge the important role of LGB parents. Numerous recommendations are identified for improving how LGB foster parents are supported within child welfare systems including foster parent and social worker training in LGB issues.     

Evaluation of the energize your life! Social marketing campaign pilot study to increase fruit intake among community college students

In this study, the authors evaluated the effectiveness of the Energize Your Life! social-marketing campaign pilot study to improve knowledge, attitudes, and fruit intake among community college students. The authors used a cross-sectional, quasi-experimental, pre- and posttest design. They randomly selected community college students (N = 1,367) and exposed the intervention campus to fruit fairs to distribute fresh fruit, 100% fruit juice, and fruit smoothie samples and information about fruit to students. The authors also addressed policy change to increase the accessibility of fruit on campus. There was a significant increase in fruit intake between pre- and posttest at the intervention campus. Although students had positive attitudes toward intake, most did not achieve the minimum recommended daily 2 servings of fruit. Approximately 25% of the students had insufficient funds, which affected their food intake. Longer-term social marketing interventions may be an effective means of improving the dietary quality of community college students.     

Regression analysis for a summed missing data problem under an outcome‐dependent sampling scheme

In this paper, we consider a regression analysis for a missing data problem in which the variables of primary interest are unobserved under a general biased sampling scheme, an outcome‐dependent sampling (ODS) design. We propose a semiparametric empirical likelihood method for accessing the association between a continuous outcome response and unobservable interesting factors. Simulation study results show that ODS design can produce more efficient estimators than the simple random design of the same sample size. We demonstrate the proposed approach with a data set from an environmental study for the genetic effects on human lung function in COPD smokers. The Canadian Journal of Statistics 40: 282–303; 2012 © 2012 Statistical Society of Canada     

Sample sizes for trials involving multiple correlated must-win comparisons

In Clinical trials involving multiple comparisons of interest, the importance of controlling the trial Type I error is well-understood and well-documented. Moreover, when these comparisons are themselves correlated, methodologies exist for accounting for the correlation in the trial design, when calculating the trial significance levels. However, less well-documented is the fact that there are some circumstances where multiple comparisons affect the Type II error rather than the Type I error, and failure to account for this, can result in a reduction in the overall trial power. In this paper, we describe sample size calculations for clinical trials involving multiple correlated comparisons, where all the comparisons must be statistically significant for the trial to provide evidence of effect, and show how such calculations have to account for multiplicity in the Type II error. For the situation of two comparisons, we provide a result which assumes a bivariate Normal distribution. For the general case of two or more comparisons we provide a solution using inflation factors to increase the sample size relative to the case of a single outcome. We begin with a simple case of two comparisons assuming a bivariate Normal distribution, show how to factor in correlation between comparisons and then generalise our findings to situations with two or more comparisons. These methods are easy to apply, and we demonstrate how accounting for the multiplicity in the Type II error leads, at most, to modest increases in the sample size.     

Design considerations in clinical trials with cure rate survival data: A case study in oncology

For clinical trials with time‐to‐event as the primary endpoint, the clinical cutoff is often event‐driven and the log‐rank test is the most commonly used statistical method for evaluating treatment effect. However, this method relies on the proportional hazards assumption in that it has the maximal power in this circumstance. In certain disease areas or populations, some patients can be curable and never experience the events despite a long follow‐up. The event accumulation may dry out after a certain period of follow‐up and the treatment effect could be reflected as the combination of improvement of cure rate and the delay of events for those uncurable patients. Study power depends on both cure rate improvement and hazard reduction. In this paper, we illustrate these practical issues using simulation studies and explore sample size recommendations, alternative ways for clinical cutoffs, and efficient testing methods with the highest study power possible.     

Moving beyond familism: Potential contributions of gerontological theory to studies of Chicano/Latino aging

Research on Chicano and Latino elders assumes that most Chicano/Latino elderly are primarily active within a family context. Familism is the most common feature of Chicano/Latino families that is used to explain the status of the elderly, how they cope with aging, and how gender dynamics among the elderly are constructed. Predictions about the future of the supportive nature of family for the elderly vary depending on how familism is conceptualized. This focus on familism is shown to be a limiting approach to Chicano/Latino aging. We illustrate how an explicit grounding in different gerontological theories directs the study of Chicano/Latino aging to include broader sociological issues. We also suggest reconceptualizing familism so that the existence of familism has theoretical as well as empirical importance. Placing research on Chicano/Latino aging into a broader sociological framework would move research away from a sociology in aging to a sociology of aging.