A measure and a graphical method for evaluating slope rotatability in response surface designs

A measure for evaluating slope rotatability over all directions in response surface designs, is proposed. This measure is used to form slope variance dispersion graph evaluating the overall slope rotatability and the slope estimation capability of an experimental design throughout the region of interest. This graph allows for an easy comparison of competing designs.     

Developments in and prospects for external debt position and burden of developing countries: The case of Korea

The delay of strong economic recovery by industrialized nations, slowed world export growth, and higher interest rates have worsened the financial situation of a number of developing countries which have relied on external borrowings to sustain current account deficits and protect economic development. Recently, well-publicized concerns over the ability to these countries to repay their considerable debt burden have been raised. To shed light on these concerns, the paper focuses on Korea—one of the heavier debt-holding countries. It describes the process through which Korea has acquired its external debt over the past decade, assesses the trends in its debt burden, and presents prospects for the period 1982–1986. Using the Korean experience, the paper shows that the most common indicators used for evaluating foreign debt burden, such as the long-term service ratio, need to be supplemented by other measurements. In a world economy characterized by short-term debts with variable interest rates, the paper suggests that an important tool in analyzing the external debt burden should be the short-term debt burden.     

Physical and Psycho-Social Predictors of Adolescents’ Suicide Behaviors

The current study examined the relationship between suicidal behaviors and physical and psycho-social predictors including body image, weight control behaviors, and risky sexual behaviors among Asian, African American, Caucasian, and Hispanic adolescents. This study used the 2007 Youth Risk Behavior Survey (YRBS). The target populations were 11,134 adolescents (5,636 female and 5,498 male) in 9th–12th grade who completed the survey. A linear regression was conducted to examine the correlation between predictors and suicidal behaviors. The results showed that gender, grade, depression, substance use, body image, weight control behaviors, and risky sexual behaviors were significant predictors of adolescents’ suicidal behaviors, while race/ethnicity was not a good predictor. Also, there were significant gender and grade differences in suicidal behaviors. Based on the results, practice implications for suicide prevention were discussed.     

Social Activity, School-Related Activity, and Anti-Substance Use Media Messages on Adolescent Tobacco and Alcohol Use

In this article, we present the effects of three hypothesized protective factors: social activities, school-related activities, and anti-substance use media messages on adolescent tobacco and alcohol use. Data were drawn from the "Monitoring the Future" (MTF) research project, which was conducted by the Institute for Social Research at the University of Michigan. The sample included 2,551 twelfth-grade students. The results of the structural equation model showed that exposure to media anti-drug messages had an indirect negative effect on tobacco and alcohol use through school-related activity and social activity. The results suggest that comprehensive ecological interventions encompassing media, family, and school can increase on the preventive effects of adolescent's substance use.     

Simple Priorities and Core Stability in Hedonic Games

In this paper we study hedonic games where each player views every other player either as a friend or as an enemy. Two simple priority criteria for comparison of coalitions are suggested, and the corresponding preference restrictions based on appreciation of friends and aversion to enemies are considered. We characterize internally stable coalitions on the proposed domains and show how these characterizations can be used for generating a strict core element in the first case and a core element in the second case. Moreover, we prove that an element of the strict core under friends appreciation can be found in polynomial time, while finding an element of the core under enemies aversion is NP-hard.     

An Efficient Operator for the Change Point Estimation in Partial Spline Model

In bioinformatics application, the estimation of the starting and ending points of drop-down in the longitudinal data is important. One possible approach to estimate such change times is to use the partial spline model with change points. In order to use estimate change time, the minimum operator in terms of a smoothing parameter has been widely used, but we showed that the minimum operator causes large MSE of change point estimates. In this paper, we proposed the summation operator in terms of a smoothing parameter, and our simulation study showed that the summation operator gives smaller MSE for estimated change points than the minimum one. We also applied the proposed approach to the experiment data, blood flow during photodynamic cancer therapy.     

A Comparison of Likelihood-Based Spatiotemporal Monitoring Methods Under Non-Homogenous Population Size

This article discusses the spatiotemporal surveillance problem of detecting rate changes of Poisson data considering non-homogenous population sample size. By applying Monte Carlo simulations, we investigate the performance of several likelihood-based approaches under various scenarios depending on four factors: (1) population trend, (2) change magnitude, (3) change coverage, and (4) change time. Our article evaluates the performance of spatiotemporal surveillance methods based on the average run length at different change times. The simulation results show that no method is uniformly better than others in all scenarios. The difference between the generalized likelihood ratio (GLR) approach and the weighted likelihood ratio (WLR) approach depends mainly on population size, not change coverage, change magnitude, or change time. We find that changes associated with a small population in time periods and/or spatial regions favor the WLR approach, but those associated with a large population favor the GLR under any trends of population changes.     

Adolescent Depression and Future Smoking Behavior: A Prospective Study

The aim of the study was to examine the associations between depressive symptoms and smoking, concurrently and prospectively, in adolescents in America, the evaluation of depressive symptoms according to different group’s smoking status, and the assessed associations between concurrent depressive level and success in smoking cessation. The participants were 2,735 boys and 2,890 girls from the Add Health data set. The prospective analysis indicated that participants with higher depressive symptoms in Wave I were more likely to start smoking and become regular smokers in Wave II. Moreover, regression analysis found that depressive symptoms in both Waves I and II predicted current smoking status. Findings are discussed within the context of the empirical and theoretical review and implications for social work practice are considered.     

Revisiting the Effectiveness of Base Crisis Response Strategies in Comparison of Reputation Management Crisis Responses

This experimental study found that employing reputation management crisis-response strategies was no better than adopting only the base crisis-response strategy (i.e., instructing and adjusting information) in terms of generating positive responses from the public. Two-sided messages (i.e., sharing both positive and negative information) in crisis communication were found to be more effective than one-sided messages in a victim crisis. In addition, even in a preventable crisis, one-sided messages (i.e., sharing only positive information) were not more effective than two-sided messages. Finally, the study found little support for Situational Crisis Communication Theory (SCCT)'s recommendations for the best crisis response strategy selections.     

I Want to Be Your Friend: The Effects of Organizations’ Interpersonal Approaches on Social Networking Sites

Publics tend to use social networking sites mainly for interpersonal communication purposes. Corporate communication focusing on promotional activities, thus, might create negative sentiments toward the organization within those platforms. This experimental study examined the effect of organizations’ interpersonal approaches to communication (e.g., nonpromotional messages, high interactivity) in social networking sites using real and fictitious companies. Our results suggest that publics consider corporate activities in social networking sites more negatively when they perceive those platforms as a personal space. However, publics evaluate an organization more positively when it is highly interactive with its publics on these platforms. Finally, publics who perceive the platform as a personal space have a more positive attitude toward the organization when the organization is both highly interactive and employs nonpromotional messages.