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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. 相似文献
54.
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. 相似文献
55.
THE INFLUENCE OF ECONOMICS ON ANTITRUST LAW 总被引:1,自引:0,他引:1
WILLIAM E. KOVACIC 《Economic inquiry》1992,30(2):294-306
Economists today play prominent roles in formulating antitrust policy and litigating antitrust cases. This paper explains why economics influences antitrust law and describes how economic theories enter and shape the antitrust system. Antitrust policy and doctrine change over time in response to developments in economic theory, and the decentralization of the antitrust adjudication system and the wide latitude accorded judges in interpreting antitrust statutes ensure that legal rules will reflect advances in the economic literature concerning the appropriate content of standards governing business conduct. 相似文献
56.
57.
In this part of the series, the notion of average total inspection (ATI) is introduced to ChSP-4A(c1, c2)r plans, minimizing ATI at a given process average, while protection to the consumer is given in terms of average outgoing quality limit and limiting quality level. The procedure is similar to that of Dodge and Roming. 相似文献
58.
Rapid advances in sociological computing are changing virtually every aspect of scholarly sociological work. These changes
offer an opportunity for sociologists to improve the quality of their work and bring new insights and approaches to bear on
important sociological problems. Nevertheless, sociologists display a profound ambivalence toward computer work by other sociologists.
Left unchecked, this ambivalence threatens to turn sociological computing into an opportunity missed. Inadequate rewards,
lack of training, and a general failure to understand the importance of computing in sociology threaten to stifle the development
of quality soft-ware, push sociologists competent in computing into other fields, and jeopardize the quality of sociological
scholarship. This article documents these ambivalent tendencies and proposes reasonable steps the discipline should take to
assure that sociological computing does not become an opportunity missed. 相似文献
59.
This study examines housing quality among three groups of single-parent women: white, African-American, and Hispanic. Three
indicators of housing quality—crowding, affordability, and satisfaction—are used to discover the extent to which these groups
experience housing problems. This study also explores differences and similarities in the factors that precipitate problems
in housing quality for these three groups of single parents. Findings suggest important differences and similarities in the
nature of housing quality problems among white, African-American, and Hispanic single-parent women. The specified variables
explained about 20% of the variance in crowding, housing affordability, and housing satisfaction. On measures of objective
and subjective housing quality, white single mothers are better housed than their African-American or Hispanic counterparts.
Hispanic single mothers have the largest housing cost burden and average more persons per household than the other groups.
African-Americans are twice as likely as either group to live in low-quality housing and reported the lowest average satisfaction
with their housing.
Her research interests include housing and neighborhood assessment and women and public policy issues. She has recently published
articles inUrban Affairs Quarterly andHousing and Society on housing and neighborhood assessment criteria among black urban households and the housing cost burden of various groups
of female-headed households. She received her Ph.D. from Ohio State University.
Her research interests include the housing adjustment behavior of women and public policy. She has recently completed her
thesis on the role of noncustodial parents in determining the quality of life of their children. She is also the recipient
of the Tessie Agan Award for research excellence from the American Association of Housing Educators for a paper titled “Unterstanding
Constraints and Residential Satisfaction among Low-Income Single-Parent Families.” 相似文献
60.
Racial differences in urban neighboring 总被引:2,自引:0,他引:2
Despite mixed expectations generated by existing theories and evidence, this analysis documents clear racial differences in urban neighboring behavior. Using data from a survey of Nashville, Tennessee, residents, we show that blacks interact with their neighbors more often than whites do, and in a greater variety of ways. The only noteworthy similarity between the two groups is the positive impact of neighboring on feelings of community affect. Overall, our results support the view that neighbor relations — like other kinds of informal participation — have helped blacks cope with constrained social opportunities and provided them with access to resources unavailable through formal institutional channels.Revised version of a paper presented at the annual meeting of the American Sociological Association, San Francisco, August 1989. 相似文献