Nonparametric covariate adjustment for receiver operating characteristic curves

The accuracy of a diagnostic test is typically characterized using the receiver operating characteristic (ROC) curve. Summarizing indexes such as the area under the ROC curve (AUC) are used to compare different tests as well as to measure the difference between two populations. Often additional information is available on some of the covariates which are known to influence the accuracy of such measures. The authors propose nonparametric methods for covariate adjustment of the AUC. Models with normal errors and possibly non‐normal errors are discussed and analyzed separately. Nonparametric regression is used for estimating mean and variance functions in both scenarios. In the model that relaxes the assumption of normality, the authors propose a covariate‐adjusted Mann–Whitney estimator for AUC estimation which effectively uses available data to construct working samples at any covariate value of interest and is computationally efficient for implementation. This provides a generalization of the Mann–Whitney approach for comparing two populations by taking covariate effects into account. The authors derive asymptotic properties for the AUC estimators in both settings, including asymptotic normality, optimal strong uniform convergence rates and mean squared error (MSE) consistency. The MSE of the AUC estimators was also assessed in smaller samples by simulation. Data from an agricultural study were used to illustrate the methods of analysis. The Canadian Journal of Statistics 38:27–46; 2010 © 2009 Statistical Society of Canada     

Insider ownership and corporate performance: evidence from Germany

In this paper we address the question whether insider ownership affects corporate performance. Evidence from studies dealing with Anglo-Saxon countries is rather inconclusive, especially because results seem to be significantly affected by endogeneity. Economically, this is due to the fact that in these countries insider ownership seems to be mainly driven by management’s compensation contracts. We argue that Germany is different in this regard, as insider ownership is often related to family control, stock-based compensation is less widespread, and the market for corporate control used to be less developed. Starting from this presumption, our data allows an unbiased observation as to whether insider ownership affects firm performance. Using a pooled data set of 648 firm observations for the years 2003 and 1998, we find evidence for a positive and significant relationship between corporate performance—as measured by stock price performance, market-to-book ratio and return on assets—and insider ownership. This relationship seems to be rather robust, even if we account for potential endogeneity by applying a 2SLS regression approach. Furthermore, the results hold for a sub-sample of firms that did not have a stock-based compensation program in place. Moreover, we find outside block ownership as well as more concentrated insider ownership to have a positive impact on corporate performance. Overall, the results indicate that ownership structure might be an important variable explaining the long term value creation in the corporate sector.

Students Left Behind: The Limitations of University-Based Health Insurance for Students With Mental Illnesses

Abstract

A growing trend in college and university health care is the requirement that students demonstrate proof of health insurance prior to enrollment. An increasing number of schools are contracting with insurance companies to provide students with school-based options for health insurance. Although this is advantageous to students in some ways, tying health insurance coverage to school enrollment can leave students vulnerable when they are most in need of help. Students whose health insurance is contingent upon their enrollment face significant lapses in coverage when they are required to leave school. This is especially challenging for students with mental illnesses whose treatment needs often go unmet in the absence of that coverage. The limitations in this system must be addressed as an increasing number of universities and students opt for university-based health insurance plans.     

Health Services Utilization Among Graduate Students: Patterns of Use,Access, and Satisfaction

Abstract

Utilization of health services by graduate students has been a neglected area of college health research. This paper describes the access problems and utilization patterns of a systematic random sample of the graduate student population at the University of Mississippi.

Survey methodology was used to assess sociodemographic, health status, and attitudinal characteristics of the study sample. In addition to type and number of visits for various health services, other utilization-related items included access to and satisfaction with care, and information received about these health services.

The results indicated that graduate students and their dependents were reliant to a large degree on local health care. Inadequacy of information was viewed as a major problem relating to access. Satisfaction with care appeared to be a function of the quality of care received.     

Response to Commentaries by Mitchell and by Butler

This paper is a response to a discussion of my work by Stephen Mitchell and Judith Butler. I treat number of issues raised by those writers. Chief among the issues raised by Mitchell are the status of drive theory and the interrelation of the intersubjective and the intrapsychic. I clarify that, although I do value the paradoxical tension between opposites in relation to many binaries, I do not aim to preserve Freud's instinct theory alongside current views of Object relations. However, I do believe that intersubjectivity theory should posit an inherent conflict in the mind that is not simply a reflection of Object relations, that is, experiences with outside others. Rather, the inherent difficulty in recognizing the other, and the attendant problems of splitting and destructiveness, are crucial aspects of intersubjective theory. Precisely for this reason I reject Butler's claim that my theory does not see destruction and breakdown as essential to the movement of recognition. I see my own intentions as closer to those expressed by Butler's own statements about the relation of destruction and recognition. However, the faith that the clinical endeavor can overcome destructiveness may be the real point of contention. Another important difference relates to the question of the triad and the third. I accept Butler's view that I emphasize the dyad over the triad and attempt to take up some of her questions about triadic relations and the nature of thirdness.     

For the Love of Fluffy: Respecting,Protecting, and Empowering Transitional Objects in the Context of High-Conflict Divorce

ABSTRACT

Transitional objects are those idiosyncratically determined, beloved blankies and stuffed animals that communicate an absent parent’s affection. As such, transitional objects serve the short-term need to cope with separation, and the long-term need to move toward autonomy. This article discusses the value, use, and misuse of transitional objects in the context of coparental conflict. The concept of alienation-by-proxy is introduced. Specific recommendations are provided, including the therapeutic creation and empowerment of transitional objects to assist children experiencing separation anxiety, consideration of the role of transitional objects in child custody evaluations, and the court’s responsibility to encourage litigating parents to respect the child’s needs for transitional objects.