An analytic method for randomized trials with informative censoring: Part 1

Consider a randomized trial in which time to the occurrence of a particular disease, say pneumocystis pneumonia in an AIDS trial or breast cancer in a mammographic screening trial, is the failure time of primary interest. Suppose that time to disease is subject to informative censoring by the minimum of time to death, loss to and end of follow-up. In such a trial, the censoring time is observed for all study subjects, including failures. In the presence of informative censoring, it is not possible to consistently estimate the effect of treatment on time to disease without imposing additional non-identifiable assumptions. The goals of this paper are to specify two non-identifiable assumptions that allow one to test for and estimate an effect of treatment on time to disease in the presence of informative censoring. In a companion paper (Robins, 1995), we provide consistent and reasonably efficient semiparametric estimators for the treatment effect under these assumptions. In this paper we largely restrict attention to testing. We propose tests that, like standard weighted-log-rank tests, are asymptotically distribution-free -level tests under the null hypothesis of no causal effect of treatment on time to disease whenever the censoring and failure distributions are conditionally independent given treatment arm. However, our tests remain asymptotically distribution-free -level tests in the presence of informative censoring provided either of our assumptions are true. In contrast, a weighted log-rank test will be an -level test in the presence of informative censoring only if (1) one of our two non-identifiable assumptions hold, and (2) the distribution of time to censoring is the same in the two treatment arms. We also extend our methods to studies of the effect of a treatment on the evolution over time of the mean of a repeated measures outcome, such as CD-4 count.     

从"权利"到"仪式":南非的艾滋病行动主义

在本文中,我考察了南非HIV/AIDS行动主义的道德政治如何有助于公民身份(citizen-ship)新形式的出现,这种新形式既与基于权利(rights-based)的斗争相关,又与个体HIV/AIDS患者对病痛和污名化(stigmatization)极端体验的共享意义相关。我指出,可以确定的是,正是晚期艾滋病患者"接近死亡"的绝境体验、以及与这种疾病晚期阶段相连的巨大污名和"社会死亡",为HIV/AIDS的幸存者对"新生命"和社会行动主义的委身提供了平台。行动主义者的干预和对这些创伤经验的重述也推动了HIV/AIDS对行动主义的委身和社会底层的动员。此外,污名和社会死亡的巨大否定性也驱使行动主义者重建对HIV检测呈阳性人群新的、正面的身份认同,并促使他们思考,作为一名公民-行动主义者和一项社会运动的成员意味着什么。     

Competitive bidding — The probability of winning

A company bidding by sealed tender needs to know the relationship between their bid price and their chances of winning the contract. Previously published models for computing the probability of winning are examined and found to be inaccurate. The problem is reformulated, and a new general predictive model for computing the probability of winning is developed. The method of computation is illustrated by a simple worked example.     

Local response to planning mandates. The prevalence and utilization of needs assessment by human service agencies.

Federal and state needs assessment mandates have traditionally been criticized both by their originators and by the local human service agencies that are required to conduct these studies as part of the planning process. This paper presents some preliminary evidence that local opposition to assessment may be shrinking as agencies gain a new appreciation for the varied uses of assessment information. Using data from a sample of Wisconsin agencies the prevalence of assessments between 1979 and 1980 is described and the conditions surrounding the practice of needs assessment are outlined. Particular attention is given to factors that affect the utilization of needs assessment results, including the characteristics of the sponsoring agency, the attributes of the study, and the structure of the assessment process.     

The economics of child care and public policy

Child care denotes any arrangement used by a working parent for care of a child, including self-care. This article is concerned with the factors that influence the demand for market modes of child care by two parent families with working mothers. A unique aspect of the study is that it is able to assess the impact of a child care subsidy program. An implication of the analysis is that the demand for market care is price elastic and is therefore susceptible to considerable change through programs of increased subsidization.     

Short- and long-term stability in organizational networks: Temporal structures of project teams

Network research focuses on patterns of stable relationships, where stability represents the unfolding of social processes over long time frames. We argue that social interactions exhibit important regularities in different time frames (short and long term), reflecting distinct social processes. We illustrate the value of this distinction through a comparative case study of technology-mediated communication, within two project teams in a digital marketing agency. We examine how the embedding of interpersonal interactions in processes of reciprocity and closure over different time horizons enables the emergence of cohesion in the face of constant compositional changes. We propose that the time frames in which stable patterns of interactions develop are the key to understanding the nature of the underlying social processes with short-term patterns of closure and reciprocity representing adaptation to change while longer term patterns indicate cohesion. Our results are supportive of this argument and show that the two teams exhibit the same regularities in interactions but across different time horizons. We discuss the implication of our findings and argue that distinguishing between short- and long-term stability of social networks offers a novel and promising avenue for network research.