Multiple event times in the presence of informative censoring: modeling and analysis by copulas

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.

     

Risk factors for child maltreatment in South Korea: An investigation of a nationally representative sample

This study investigated the risk factors associated with the occurrence of child physical and psychological abuse in South Korea based on the ecological theory of child maltreatment. A subsample of 3‐ to 18‐year‐old children from “A Study on the Current State of Child Abuse and Neglect,” a nationally representative study on child abuse and neglect, was utilized for secondary data analysis. The sample was divided into two age groups (third graders in elementary school and below and fourth graders and above). We utilized hierarchical logistic regression for each age group separately to analyze the data. The variables at each level of the system (i.e., ontogenic development, microsystem, and exosystem) were entered into the model in sequential order. The results showed the common risk factors for both age groups are the caregiver's experience of abuse in childhood, the child's problem behavior, exposure to domestic violence, community size, and informal social control. The child's age was also significant in both groups but in the opposite direction. Social support was a significant predictor for the younger age group only, while the caregiver's level of education was significant for the older age group only. Implications for future research and practice are discussed based on the study results.     

Low dose risk estimation via simultaneous statistical inferences

Summary.  The paper develops and studies simultaneous confidence bounds that are useful for making low dose inferences in quantitative risk analysis. Application is intended for risk assessment studies where human, animal or ecological data are used to set safe low dose levels of a toxic agent, but where study information is limited to high dose levels of the agent. Methods are derived for estimating simultaneous, one-sided, upper confidence limits on risk for end points measured on a continuous scale. From the simultaneous confidence bounds, lower confidence limits on the dose that is associated with a particular risk (often referred to as a bench-mark dose ) are calculated. An important feature of the simultaneous construction is that any inferences that are based on inverting the simultaneous confidence bounds apply automatically to inverse bounds on the bench-mark dose.     

Benchmark Analysis: Shopping with Proper Confidence

We discuss the issue of using benchmark doses for quantifying (excess) risk associated with exposure to environmental hazards. The paradigm of low-dose risk estimation in dose-response modeling is used as the primary application scenario. Emphasis is placed on making simultaneous inferences on benchmark doses when data are in the form of proportions, although the concepts translate easily to other forms of outcome data.     

Zimbabwe's AIDS action programme for schools

AIDS education started very early in Zimbabwe and is now compulsory in all schools. This evaluation documents the development of the primary and secondary school AIDS Action Programme from 1991 to 1998. Six programme aspects were evaluated: programme start-up, planning and management, development of syllabi and materials, teacher training, research, monitoring and evaluation, and co-ordination. The Programme drew on resources from within the existing educational system. Due to broad-based consultation and participation, it was supported by Government and partners. Flexible management ensured implementation of mid-course corrections. It was concluded that school AIDS programmes should stress participatory teaching and learning methods and life-skills training. Curriculum writers and teachers needed training and supervision in participatory techniques. Cluster workshops between district and school levels were needed to strengthen the cascade model of teacher training that had been adopted. Systematic research, monitoring and evaluation were essential, including follow-ups to baseline surveys. The Zimbabwean programme was well-designed, relatively inexpensive and replicable.     

Factors Associated with Having Flextime: A Focus on Married Workers

To examine flexible work scheduling of married workers a conceptual framework was developed and tested using the 1997 Current Population Survey Work Schedules Supplement. Odds of flextime use were higher for married males, non-Hispanic whites, those with relatively higher levels of education and income, those with a preschool aged child, residents of the Midwest or West (as compared with the South), managers or professionals, and employees of the federal government.     

The transition to parenthood in Puerto Rico: Occupational status and the timing of first births

This study examines the relationship between occupational status and fertility timing during a period of rapid development in Puerto Rico. Our fundamental hypothesis is that women with higher status occupations face greater opportunity costs than those with less valued jobs and therefore will be more likely to postpone parenthood until later ages than women without such high costs. We test this hypothesis using event history techniques with data from the 1982 Puerto Rico Fertility and Family Planning Assessment, an island-wide survey of women between the ages of 15 and 49. The analysis examines the effects of occupational status on the timing of first births, and finds strong support for the basic hypothesis, especially regarding the post-ponement of teen births. After the teen years, the effects are less pronounced. Overall, it appears that employment opportunities have played an important role in childbearing decisions in Puerto Rico.An earlier version of this paper was presented at the annual meeting of the Population Association of America, Denver, Colorado, 30 April–2 May 1992.     

Sex differences in nonverbal expressiveness: Emotional expression,personality, and impressions

Sex differences in expressiveness are well documented, but the reasons for and correlates of these important differences are not well studied. A comprehensive set of emotion-relevant personality measures was administered to 40 female and 39 male undergraduate participants, who were also videotaped in three situations: engaging in natural social interaction, describing a past emotional experience, and posing various emotions. Videotapes were judged by sets of naive observers as to emotion communicated and overall impression. Expressive females, who appeared friendly and dominant in social interaction, were found to have a hostile/aggressive personality (but this was not true of males). Expressive females also tended to look angry/disgusted when describing happy and sad experiences. The findings suggest that nonverbally skilled, charismatic women (but not men) may often possess a dominant/aggressive but self-controlled personality, in a new twist on the theory that sex differences in expressiveness result in part from the oppression of women in society.This research was supported in part by an intramural research grant from University of California, Riverside.     

The Future of ‘Gender and Organizations’: Connections and Boundaries

‘Gender and organizations’, a fruitful connection between two previously separate areas of study, has had a relatively short but bountiful history. Much of the research and theorizing within the general rubric of ‘gender and organizations’ has required the breaking of conceptual boundaries and the forging of new connections that go beyond the coalescence of two fields of inquiry. We have not exhausted the possibilities suggested by broken boundaries and new connections. This may be a particularly auspicious time to be breaking boundaries, for the apparent worldwide changes in work and organizing are not well enough understood with many of our old intellectual tools. In this paper I discuss briefly what our studies of gender and organization have, in my view, accomplished so far, and then review some issues and questions stimulated by thinking about broken boundaries and new connections, possibilities that, for me, represent part of the future for ‘gender and organizations.’