The analysis of incomplete data using stochastic covariates

In the development of many diseases there are often associated random variables which continuously reflect the progress of a subject towards the final expression of the disease (failure). At any given time these processes, which we call stochastic covariates, may provide information about the current hazard and the remaining time to failure. Likewise, in situations when the specific times of key prior events are not known, such as the time of onset of an occult tumour or the time of infection with HIV-1, it may be possible to identify a stochastic covariate which reveals, indirectly, when the event of interest occurred. The analysis of carcinogenicity trials which involve occult tumours is usually based on the time of death or sacrifice and an indicator of tumour presence for each animal in the experiment. However, the size of an occult tumour observed at the endpoint represents data concerning tumour development which may convey additional information concerning both the tumour incidence rate and the rate of death to which tumour-bearing animals are subject. We develop a stochastic model for tumour growth and suggest different ways in which the effect of this growth on the hazard of failure might be modelled. Using a combined model for tumour growth and additive competing risks of death, we show that if this tumour size information is used, assumptions concerning tumour lethality, the context of observation or multiple sacrifice times are no longer necessary in order to estimate the tumour incidence rate. Parametric estimation based on the method of maximum likelihood is outlined and is applied to simulated data from the combined model. The results of this limited study confirm that use of the stochastic covariate tumour size results in more precise estimation of the incidence rate for occult tumours.     

Gender-specific changes in students' sexual behaviors and attitudes at a southeastern university between 1973 and 1988.

This study investigated the gender-specific, self-reported sexual behaviors and attitudes of never-married college students attending a southeastern university in 1973 and 1988. Data were collected by means of a mailed questionnaire that remained essentially unchanged for both years. The authors found that both men and women reported an increase in heterosexual relationships that included sexual intercourse and a decrease in nonsexual relationships with the other gender. The majority of the students perceived themselves as adequately informed about sexuality and satisfied with their relationships, although the proportion of men who reported being satisfied with their relationships declined over the 15 years. The students indicated that sexuality education should focus primarily on information about AIDS and on preparation for marriage.     

Testing for state and local government job queues

Bivariate probit estimates with partial observability identify the factors influencing the worker’s decision to seek a state or local government job and the factors influencing the government’s decision to hire particular workers. The estimates routinely confirm the presence of a local job queue but confirm the presence of a state job queue only when the role of unionization is explicitly recognized. Our results suggest that the net benefits from local and state government employment are greater than those from private sector employment. The estimates also indicate that local governments disproportionately hire racial minorities relative to the local governments’ pool of applicants but indicate no such relationship for state governments. The authors thank Dale Belman, Jugal Ghorai, and Matt Higgins for help on this and related work. We also thank the referee and the editor for useful suggestions.     

A-OPTIMAL RUN ORDERS WITH A LINEAR TREND

A-optimal ran orders are considered in the presence of a linear trend with emphasis on non-orthogonal situations where no trend-free run order can be. A-optimal. Some possibilities for further extension are also briefly indicated.     

城市可持续发展中的文化指标

本文为第三届“文化与城市可持续发展”国际会议的主题发言。本文介绍了会议背景 ,论述了文化及其与可持续发展的关系 ,都市化进程及其发展方向等问题 ,并着重阐述了本次会议的主题即“城市可持续发展中的文化指标” ,确立了本次会议的总体基调和基本政策     

A response to “the emotional consequences of physical child abuse” by Annaclare van Dalen

The author responds to the article by Annaclare van Dalen (1989), disputing her statement that there is little in the literature about the emotional consequences of child abuse. The author reviews the pertinent literature, which is abundant. The author disagrees with van Dalen's statement that the child experiences physical abuse outside the body, and with the statement that the child experiences sexual abuse as pleasurable. In addition the author disagrees with van Dalen's sharp differentiation between physical abuse and sexual abuse, and proposes that sexual abuse be regarded as a variant of physical abuse.     

A simultaneous-equations model of the relationship between public sector bargaining legislation and unionization

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.