Substance abuse, suicidality, and self-esteem in South African adolescents

Associations among six different domains of self-esteem (peers, school, family, sports/athletics, body image, and global self-worth) and risk behaviors related to substance use and suicidality were investigated in a sample of South African adolescents. Students enrolled in Grades 8 and 11 at independent secondary schools in Cape Town (N = 116) completed the Self-Esteem Questionnaire (SEQ) and a questionnaire that asked about their participation in a range of risk behaviors. Logistic regression analyses indicated that particular domains of self-esteem were differentially associated with indicators of alcohol, cigarette and drug use and suicidal ideation or behaviors in adolescents. Family self-esteem showed the strongest overall pattern of associations with the risk behaviors. Overall, the findings of this study suggest that interventions which aim to protect adolescents from engaging in risk behaviors by increasing their self-esteem are likely to be most effective and cost-efficient if they are aimed at the family and school domains.     

Chartering strategies for shipping companies

This paper describes a model which may be used in the evaluation of the relative effectiveness of policies used in the areas of ship chartering and the switching of combined carriers between the dry cargo market and the tanker market. The policies for chartering and market switching are expressed in the form of ‘desired proportions’ of the fleet operating in a particular charter-mode or a particular market. Graphical illustration of this form of expression of policies can be easily understood, so that alternative policies can be designed with relative ease. The effectiveness of a particular form of policy under various freight market conditions can be determined from the model, the use of which is illustrated by its application to the deployment of the fleet of an hypothetical shipping company. It is assumed that the feedback connection between the company's actions and the marketplace is negligible.     

Substance Use and Psychosocial Predictors of High School Dropout in Cape Town, South Africa

The aims of this study were to examine whether use of tobacco, alcohol, and illicit drugs predicts dropout among secondary school students in Cape Town, South Africa. A self-report instrument was administered to 1,470 Grade 8 students. The proportion of students that dropped out of school between the onset of the study and 4 years later was 54.9%. After adjusting for a range of confounders, dropout was significantly predicted by absenteeism, poverty (as assessed by a possession index), and past month cigarette use, but not by past month alcohol use and lifetime illicit drug use. Contrary to findings from developed countries, alcohol and illicit drug use did not predict dropout. It is possible that predictors of dropout documented elsewhere may not be pertinent in developing countries.     

Exchange curves for fixing batch quantities

The problem considered is that of choosing batch quantities to minimize costs, subject to the constraints that neither overall set-up costs nor overall set-up time can be increased beyond certain limits. Theoretical and graphical solutions are obtained for two possible formulations of the problem, and a simple practical procedure is suggested.     

Rates of missing responses in personal digital assistant (PDA) versus paper assessments

This article describes rates of missing item responses in personal digital assistant (PDA) assessments as compared to paper assessments. Data come from the evaluation of a classroom-based leisure, life skills, and sexuality education program delivered to high school students in Cape Town, South Africa. Analyses show that the paper assessments had much higher rates of missing-ness than PDA assessments. This association is moderated by item order. Certain analyses also suggest that paper assessments have higher rates of missingness for items pertaining to participants' sexual behavior. Implications of these results for evaluation research will be discussed.     

Measurement of risk and protective factors for drug use and anti-social behavior among high school students in South Africa

The study sought to examine, for South African adolescents: 1) the reliability of sub-scales of the Communities that Care Youth Survey (CTC Youth Survey) of risk and protective factors for drug use and anti-social behavior; and 2) the extent to which tobacco, alcohol and marijuana use can be predicted from community, family, school, and peer-individual factors based on sub-scales of the CTC Youth Survey. On two occasions, 92 male and 31 female, Grade 8 and 11 students completed measures concerning: 1) their past month tobacco, alcohol and marijuana use; and 2) various community, family, school, and peer-individual factors. Cronbach alpha coefficients of sub-scales of the questionnaire ranged between .60 and .94. Kappa values were at least moderate (above .40) on 19 sub-scales, and on the remaining sub-scales observed agreement levels ranged between .49 and .94. Each domain predicted tobacco, alcohol, and marijuana use. Multiple logistic regression analyses revealed that alcohol use was most strongly accounted for by the peer domain, tobacco use by the school domain, and marijuana use by the peer and community domains. The findings support use of the CTC Youth Survey, with slight revisions, among South African high school students.