Confidence Intervals for the Youden Index and Corresponding Optimal Cut-Point

A global measure of biomarker effectiveness is the Youden index, the maximum difference between sensitivity, the probability of correctly classifying diseased individuals, and 1-specificity, the probability of incorrectly classifying healthy individuals. The cut-point leading to the index is the optimal cut-point when equal weight is given to sensitivity and specificity. Using the delta method, we present approaches for estimating confidence intervals for the Youden index and corresponding optimal cut-point for normally distributed biomarkers and also those following gamma distributions. We also provide confidence intervals using various bootstrapping methods. A comparison of interval width and coverage probability is conducted through simulation over a variety of parametric situations. Confidence intervals via delta method are shown to have both closer to nominal coverage and shorter interval widths than confidence intervals from the bootstrapping methods.     

Student Participation in Study Abroad Programs: Social Justice Implications for Tertiary Education

ABSTRACT

Short-term study abroad programs are increasingly embraced by Australian schools of social work. These programs improve access to international experiences and have a demonstrable impact on academic outcomes. However, little is known about the factors that influence students who decide to participate in such programs. Using a qualitative semistructured design, eight Australian social work students were interviewed about their perspectives on the pre-application phase of a short-term study abroad program to Ireland that was advertised in early 2018. The findings reveal a number of multilevel structural, institutional, and personal enablers and barriers that impacted their decision to participate. Implications for future research, the tertiary education sector, and social work educators are identified, especially in terms of broader economic and political issues that contradict social justice and render the future of these programs precarious.

IMPLICATIONS

• Short-term study abroad programs offer important learning opportunities for students, but there is a need to understand the dimensions that can impact the decisions of students to participate in these programs.

• The qualitative findings indicate that various factors impact on the participation of students, especially financial and caring responsibilities.

• Further research that is underpinned by a social justice lens is needed to address inequities in student participation.

     

Reality check. Evaluating a school-based gang prevention model

The Gang Resistance Education and Training (G.R.E.A.T.) program is a school-based gang prevention initiative developed in 1991 through the collaborative efforts of the Bureau of Alcohol, Tobacco, and Firearms, the Federal Law Enforcement Training Center, and the Phoenix Police Department. Uniformed law enforcement officers, certified as G.R.E.A.T. instructors, teach the 9-week curriculum to middle students. In 1994, the National Institute of Justice funded a national evaluation of the G.R.E.A.T. program. The process evaluation component of this larger study is reported. First, results of on-site observations of the G.R.E.A.T. Officer Training program, including an overview of the training activities, and the authors' assessment of the training process are reported. Second, observations of the implementation of the program by officers at six sites are reported. Of primary concern was whether the program delivered to students was similar to the program taught to the officers during the G.R.E.A.T. Officer Training.     

Measuring community mobilization in the Seattle Minority Youth Health Project.

This article assesses the validity and reliability of the approach used to measure community mobilization in the Seattle Minority Youth Health Project (MY Health), a neighborhood-based program to prevent drug use, violence, teen pregnancy, and sexually transmitted diseases (STDs). Two constructs were measured: neighborhood cooperation in solving problems, and sense of pride and identification with the neighborhood. The convergent validity of the measurement approach was assessed by comparing several independent measures of community mobilization generated from surveys of key neighborhood leaders, youth, and parents. For the neighborhood cooperation construct, correlations were uniformly positive across measures from different surveys and statistically significant about a quarter of the time. The correlations for the neighborhood pride construct were weaker and generally not statistically significant. Interrater reliability was low for all of the surveys, possibly reflecting varying ideas about what community mobilization meant among survey respondents.     

Economics, law, and covenant marriage

Covenant marriage may be difficult to understand as a gender issue. However, marriage and divorce are closely linked to workforce participation and child rearing. This piece looks at new proposals for choices in divorce regime from legal, economic, and social perspectives, concluding that the option of contracting a more permanent form of marriage increases the possibilities for women and signals societal interest in promoting more stable families. The article favorably compares Louisiana covenant marriage legislation to other states' suggestions for returns to fault-only regimes, and pays some attention to the role one state's marriage and divorce laws play in the federal system.     

Bayesian MARS

A Bayesian approach to multivariate adaptive regression spline (MARS) fitting (Friedman, 1991) is proposed. This takes the form of a probability distribution over the space of possible MARS models which is explored using reversible jump Markov chain Monte Carlo methods (Green, 1995). The generated sample of MARS models produced is shown to have good predictive power when averaged and allows easy interpretation of the relative importance of predictors to the overall fit.     

Discrete distributions with maximum expected value of the maximum

We give an upper bound for the expected value of the largest order statistic of a simple random sample of size n from a discrete distribution on N points. We also characterize the distributions that attain such bound. In the particular case n=2, we obtain a characterization of the discrete uniform distribution. © 1998 Elsevier Science B.V. All rights reserved.     

Failure Inference From a Marker Process Based on a Bivariate Wiener Model

Many models have been proposed that relate failure times and stochastic time-varying covariates. In some of these models, failure occurs when a particular observable marker crosses a threshold level. We are interested in the more difficult, and often more realistic, situation where failure is not related deterministically to an observable marker. In this case, joint models for marker evolution and failure tend to lead to complicated calculations for characteristics such as the marginal distribution of failure time or the joint distribution of failure time and marker value at failure. This paper presents a model based on a bivariate Wiener process in which one component represents the marker and the second, which is latent (unobservable), determines the failure time. In particular, failure occurs when the latent component crosses a threshold level. The model yields reasonably simple expressions for the characteristics mentioned above and is easy to fit to commonly occurring data that involve the marker value at the censoring time for surviving cases and the marker value and failure time for failing cases. Parametric and predictive inference are discussed, as well as model checking. An extension of the model permits the construction of a composite marker from several candidate markers that may be available. The methodology is demonstrated by a simulated example and a case application.     

The Zen of physician initiatives

Many physicians today feel ravaged by the brutal speed with which change has been occurring. They see the beliefs and practices of a lifetime being abandoned and replaced by the flavor of the month, management du jour. But if you are willing and able to take the brave step of approaching your physicians without an agenda, meeting with them to listen to their concerns, and can also avoid hanging a lightning-rod label on every bright new idea that comes out of the sessions, you'll be on the way to effective new management. This new style is a "Zen" approach (but don't give it that label) that lets real collaboration come into the place that is supposed to be all about healing--the health care organization. From "never call it anything" to "stay with them until they get it," ideas on how to be a Zen manager are presented, with the ultimate goal of truly partnering with physicians and infusing them with a desire to move beyond the frustration and disenchantment they are feeling.