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.     

Estimating the Rayleigh distribution scale parameter from doubly censored samples—Some comments

In a recent paper in this journal, Lee, Kapadia and Brock (1980) developed maximum likelihood (ML) methods for estimating the scale parameter of the Rayleigh distribution from doubly censored samples. They reported convergence difficulties in attempting to solve numerically the nonlinear likelihood equation (LE). To mitigate these difficulties, they employed approximations to simplify the LE, but found that the solution of the resulting simplified equation can give rise to parameter estimates of erratic accuracy. We show that the use of approximations to simplify the LE is unnecessary. In fact, under suitable parametric transformation, the log-likelihood function is strictly concave, the ML estimate always exists, is unique and finite. Furthermore, the LE is easy to solve numerically. A numerical example is given to illustrate the computations involved.     

Benefits of preventive dentistry in children: Cost factors and public policy

Dental caries in children is now recognized as a preventable disease. The use of fluoride and sealants has produced a major reduction in caries prevalence among school aged children in the United States and other countries. A portion of the child population who are educationally and socioeconomically disadvantaged are not fully receiving these benefits. Public policy, insurance and medicaid groups must be made aware of these preventative measures and strategies developed to implement them.     

Cognitive and interpersonal abilities related to the primary activities of R&D managers

This study attempted to identify the primary activities performed by R&D managers at different supervisory levels, and the cognitive and interpersonal ability requirements that underlie these activities. A task inventory containing 244 managerial tasks was completed by 117 R&D managers in nine organizations. The 48 tasks which managers rated as having spent the most time were factor analyzed, resulting in the identification of three primary activities: project management, personnel supervision, and strategic planning. Furthermore, these activities varied with supervisory level, with R&D managers performing a wider range of these activities with the progression from first-line to upper-level management.Thirty R&D managers later rated the degree to which 19 cognitive and interpersonal abilities were required for performing these primary activities. Strategic planning was rated as requiring significantly higher levels of oral expression, logical reasoning, originality, fluency of ideas, oral defense, and resistance to premature judgement than was required for the other two primary activities. Personnel supervision required a higher level of social sensitivity than was required for the other two activities. Project management required high levels of information ordering, oral fact- finding ability, problem sensitivity, and oral and written comprehension. Implications of the findings for understanding R&D managerial performance and personnel staffing functions are discussed.     

MOVING OUT OF THE HOUSE: AN ANALYSIS OF CONGRESSIONAL QUITS

Despite extensive study concerning involuntary departures by U.S. House members, little has been said about voluntary departures from the House–-quit behavior. This paper has three primary purposes: (1) to establish a theoretical framework that models the full range of choices a representative faces in any given term, (2) to measure the impact of different variables that affect representatives' quit behavior, and (3) to explain why Republicans have been more likely to pursue higher office than their Democratic colleagues.     

The State of Care Management in Learning Disability and Mental Health Services 12 Years into Community Care

This paper reports on the organization of care management froma longitudinal study of community care for people resettledfrom long-stay learning disability and psychiatric hospitals.The findings from a 12-year follow-up of care management arrangementsin 12 learning disability and eight mental health study siteservices are described. The diversity of care management arrangementsfound at earlier points in the evaluation remained evident.Also, many of the former ‘care in the community’service users were excluded from mainstream care managementarrangements in their localities. The difficulty of developingperson-centred arrangements in learning disability and the lackof integration of the Care Programme Approach and care managementwere evident. The findings and observations are placed in thewider policy and practice context, with suggestions for takingcare management forward nationally and locally.     

Feminism,militarism, and attitudes toward the role of women in the military

Attitudes toward the role of women in the military require the reconciliation of two often conflicting beliefs: those toward the roles and rights of women and those toward the military. This article explores the relationships between positive attitudes toward women’s roles throughout society, or feminism, and positive attitudes toward defense spending, or militarism, both with each other and with attitudes toward gender integration in the military. Results of this analysis show there to be a negative relationship between feminism and militarism, a positive relationship between feminism and gender integration, and a negative relationship between militarism and gender integration. The results of multiple regression analysis show that feminism is the strongest predictor of attitudes toward gender integration, while militarism is weak in its predictive ability. The author argues that the issue of women in the military is more one of women’s equality than of national defense and that policy discussions should be structured accordingly. She is currently conducting research which examines how women in the United States military employ strategies to manage gender and sexuality. This research provides evidence for the claim that gender is not simply a role or an attribute, but that gender is created and recreated through our interactions with others.     

The gambling lifestyle: I. theory

This paper describes the lifestyle model of gambling behavior in which compulsive gambling behavior is conceptualized as a lifestyle characterized by pseudoresponsibility, self-ascension, hypercompetitiveness, and social rule breaking/bending/ twisting. The underlying premise of this theory is that gambling behavior takes on the appearance of a lifestyle when it is viewed by the individual as a viable means of enhancing self-worth, minimizing personal insecurity, and controlling fear. Three primary areas of theoretical and research interest are covered in this paper: (1) the theoretical underpinnings of lifestyle theory; (2) the individual components (conditions, choice, cognition) of a gambling lifestyle; and (3) the developmental progression of a gambling lifestyle.The author would like to thank Henry Lesieur and anonymous reviewers of earlier versions of this paper for their helpful comments. The assertions and opinions contained herein are the private views of the author and should not be construed as official or as reflecting the views of the Federal Bureau of Prisons or United States Department of Justice.