On Non-parametric Estimation of the Survival Function with Competing Risks

The non-parametric maximum likelihood estimators (MLEs) are derived for survival functions associated with individual risks or system components in a reliability framework. Lifetimes are observed for systems that contain one or more of those components. Analogous to a competing risks model, the system is assumed to fail upon the first instance of any component failure; i.e. the system is configured in series. For any given risk or component type, the asymptotic distribution is shown to depend explicitly on the unknown survival function of the other risks, as well as the censoring distribution. Survival functions with increasing failure rate are investigated as a special case. The order restricted MLE is shown to be consistent under mild assumptions of the underlying component lifetime distributions.     

Leadership ambiguity in universities and K–12 schools and the limits of contemporary leadership theory

This paper explores the differences in context, assumptions, and behavior of leaders both in modern American universities and in elementary and high schools. The paper's main section examines the utility of five leadership theories (situational, charismatic, transformational, path–goal, and leader–member exchange [LMX]) in explaining leader behavior in each educational sector. We show that while each theory has some merit, none adequately incorporates the larger internal and external “system” pressures on leaders whose institutions are undergoing changes. The paper concludes with a recommendation for a reformulation of the leadership dilemmas in education that sets the five theories in a broader, systemic conceptual framework.     

Leaving Home for College: Expectations for Selective Reconstruction of Self

This paper describes how 23 primarily upper-middle-class high school seniors anticipated identity changes as they prepared to leave home for college. The transition from high school to college is a period of “liminality” during which students are structurally in between old and new statuses. We discuss how students anticipated change, planned to affirm certain of their identities, imagined creating new identities, and contemplated discovering unanticipated identities. Such interpretive effort must be understood in the context of the ambivalence they felt about leaving home and achieving independence. The data also provoke discussion of how social class membership might be implicated in people's ability to control identity change as they move through the life course.     

Changing the Palace Guard: Analysing the Impact of Women's Entry into Medicine

Women's rapid entry into medicine raises important questions about change in this historically male-dominated profession. In addition to shifting the gender balance, do increasing numbers of women signal a more fundamental change in the way in which medicine is organized and practised? A growing body of research suggests such change. Yet there is continuing controversy about the meaning of observed gender differences in practice, whether they reflect an essentially pragmatic response to women's dual workload of family and career, or whether they are the result of underlying differences in attitudes, values and orientations. This article uses data from a survey of a recent cohort of family physicians in Ontario, Canada, to document the extent of gender differences and similarities in medical practice, and their interrelationships to family situation, political attitudes and patient care attitudes. The results show that seemingly related differences in practice are accounted for in different ways: while some are associated with differences in family situation, others are tied to attitudes, while others are a function of gender alone. The results also reveal gender similarities which do not suggest that women are becoming more like men, but that men, and the profession as a whole are changing. We would emphasize the importance of interpreting gender differences and similarities within a broader conceptual understanding of change in the profession.     

Evolutionary politics? Union differences and political activities in the 1990s

Conclusion The political environment faced by U.S. unions has changed substantially over the past decade. The cost of election campaigns has increased dramatically and many interest groups have become actively involved in election financing. More importantly, the election of a Republican majority to Congress in 1994 caused a major change in the nature of unions' interactions with Washington legislators. Organized labor has faced a barrage of bills aimed at reducing the power of unions and minimizing their political involvement. Such efforts have also occurred across the country as conservative groups have attempted to qualify referenda that limit unions in some way. At a time when unions must organize new workers to survive as a viable force in society, these political challenges are especially serious matters.     

The graphical advantages of finite interval confidence band procedures

When presented as graphical illustrations, regression surface confidence bands for linear statistical models quickly convey detailed information about analysis results. A taut confidence band is a compact set of curves which are estimation candidates for the unobservable, fixed regression curve. The bounds of the band are usually plotted with the estimated regression curve and may be overlaid by a scatter-plot of the data to provide an integrated visual impression. Finite-interval confidence bands offer the advantages of clearer interpretation and improved efficiency and avoid visual ambiguities inherent to infinite-interval bands. The definitive characteristic of a finite-interval confidence band is that it is only necessary to plot it over a finite interval in order to visually communicate all its information. In contrast, visual representations of infinite-interval bands are not fully informative and can be misleading. When an infinite-interval band is plotted, and therefore truncated, substantial information given by its asymptotic behavior is lost. Many curves that are clearly within the plotted portion of the infinite interval confidence band eventually cross a boundary. In practice, a finite-interval band can always be easily obtained from any infinite-interval band. This article focuses on interpretational considerations of symmetric confidence bands as graphical devices.