Modelling human immunodeficiency virus ribonucleic acid levels with finite mixtures for censored longitudinal data

The measurement of human immunodeficiency virus ribonucleic acid levels over time leads to censored longitudinal data. Suitable models for dynamic modelling of these levels need to take this data characteristic into account. If groups of patients with different developments of the levels over time are suspected the model class of finite mixtures of mixed effects models with censored data is required. We describe the model specification and derive the estimation with a suitable expectation-maximization algorithm. We propose a convenient implementation using closed form formulae for the expected mean and variance of the truncated multivariate distribution. Only efficient evaluation of the cumulative multivariate normal distribution function is required. Model selection as well as methods for inference are discussed. The application is demonstrated on the clinical trial ACTG 315 data.     

WILL GIRLS BE GIRLS? RISK TAKING AND COMPETITION IN AN ALL‐GIRLS' SCHOOL

We conduct an experiment that examines the relationship between girls only schooling and risk taking and competitive behavior. In it, we compare decisions made by students in an all‐girls' school to those made by students in a closely matched coeducational school. We further investigate the developmental nature of this behavior by comparing choices made by younger students (Grades 7 and 8) with those of older students (Grades 11 and 12). We focus on the differences between those who select into the all‐girls' school, and find that although girls educated in a single sex environment are the most risk averse, they are also among the most competitive. These results lend texture to the hypothesis that “nurture matters” in the gender differences debate. (JEL C93, J16, I21)     

Dimensions of Social Stratification and Their Relation to Mortality: A Comparison Across Gender and Life Course Periods in Finland

Social Indicators Research - Differences in mortality between groups with different socioeconomic positions (SEP) are well-established, but the relative contribution of different SEP measures is...     

Vision and state health department public relations practitioners: Prepared to lead?

Visions are important to organizational effectiveness. Although providing vision has been identified as one of the behaviors that best captures organization-wide public relations leadership, little public relations research has focused on vision. Similarly, state health departments have drawn little interest among public relations scholars even though states are a central part of the nation's public health system. This study addressed the perceptions of the top public relations professionals at state health departments concerning vision and their involvement in the visioning process. The practitioners were nearly unanimous in their belief that organizational visions are important. However, results indicate that some top public relations practitioners at state health departments are not prepared to make optimal contributions to the visioning process. In order to take full advantage of opportunities to serve as organization-wide leaders, public relations practitioners should seek out information about visioning in order help chart their organization's future and enhance their careers.     

Efficacy of Statistical Outlier Analysis for Monitoring Quality of Care

Researchers have proposed that hospitals with excessive statistically unexplained mortality rates are more likely to have quality-of-care problems. The U.S. Health Care Financing Administration currently uses this statistical “outlier” approach to screen for poor quality in hospitals. Little is known, however, about the validity of this technique, since direct measures of quality are difficult to obtain. We use Monte Carlo methods to evaluate the performance of the outlier technique as parameters of the true mortality process are varied. Results indicate that the screening ability of the technique may be very sensitive to how widespread quality-related mortality is among hospitals but insensitive to other factors generally thought to be important.