Identification of Influential Cases in Kernel Fisher Discriminant Analysis

We study the influence of a single data case on the results of a statistical analysis. This problem has been addressed in several articles for linear discriminant analysis (LDA). Kernel Fisher discriminant analysis (KFDA) is a kernel based extension of LDA. In this article, we study the effect of atypical data points on KFDA and develop criteria for identification of cases having a detrimental effect on the classification performance of the KFDA classifier. We find that the criteria are successful in identifying cases whose omission from the training data prior to obtaining the KFDA classifier results in reduced error rates.     

Time-on-task, technology and mathematics achievement

Information and communication technologies hold much promise for use in education in developing countries. This study reports on an evaluation conducted on the introduction of computers in the delivery of the mathematics curriculum in one of the provinces of South Africa. Although the request was for an outcome evaluation very early in the implementation of the program, it was tailored in such a way as to fulfill a more formative role. Despite substantial variability in implementation, and in most cases with very weak exposure of the learners to the intervention, sufficient evidence emerged to indicate that this mode of curriculum delivery may be effective. Improvement in mathematics performance was related to a range of variables: some concerned classroom teaching practices, some referred to social differences between the learners, and some to the specific intervention. The strongest of these predictors in the sample was the strength of the intervention: the more time learners spent on using the software to study mathematics, the more improvement they showed from 1 year to the next in their performance in the subject.     

Advancing human rights through constitutional protection for gays and lesbians in South Africa

As a consequence of the 1994 adoption of a justiciable Bill of Rights in South Africa, with an equality provision prohibiting discrimination on the ground of sexual orientation, a coalition of gay and lesbian organisations set about implementing a progressive agenda of gay and lesbian rights litigation. In striking down the offence of sodomy, the Constitutional Court established a jurisprudence of gay and lesbian rights to equality, dignity and privacy that proved to be the foundation for significant litigation around family law issues. Subsequent to the sodomy judgement, the Court has ruled that same-sex couples who are in permanent life partnerships should be entitled to the same rights as married couples to immigration, employment benefits, custody and adoption of children. Despite the extensive equality jurisprudence of the Court, it is still uncertain whether it will rule in the future in favour of same-sex marriage or in favour of a civil union/domestic partnership model.     

Variable Selection for Kernel Classification

In this article, a variable selection procedure, called surrogate selection, is proposed which can be applied when a support vector machine or kernel Fisher discriminant analysis is used in a binary classification problem. Surrogate selection applies the lasso after substituting the kernel discriminant scores for the binary group labels, as well as values for the input variable observations. Empirical results are reported, showing that surrogate selection performs well.     

Evaluation in South Africa: An introduction

This article provides a brief background to the articles in this edition on evaluation in South Africa. The overall background is self-evident: South Africa is a country which has undergone a political revolution, with a government of national unity in place. The formulation and implementation of new policies, and the programs which form part of them, will be an important part of South African politics in the years to come.These articles also appear against the more immediate background of trying to place evaluation on a surer footing in this country. In this introduction the efforts of a group of South African evaluators to position themselves and their activities in such a way as to make evaluation an accepted part of the organizational landscape, and to play a useful role in a future South Africa, are described as well.     

Alcohol and drug abuse: removing structural barriers to treatment for historically disadvantaged communities in Cape Town

The article reports on an exploratory study that examined access to alcohol and other drug treatment for historically disadvantaged communities in the Cape Town metropole. In-depth interviews were conducted with 20 key informants from various sectors of the alcohol and drug treatment system, including treatment service providers, members of local drug action committees and social workers from district social service offices. Findings highlighted three structural barriers to service delivery: (i) difficulties in developing and implementing a strategic plan relating to alcohol and drug problems due to poor capacity and other infrastructural issues, such as a lack of information, poor intersectoral collaboration and limited consultation with service providers; (ii) limited allocation of resources to alcohol and drug treatment which has restricted the availability of affordable services as well as the capacity of established services to meet increased demand for services in this area; and (iii) fragmented service delivery. The study highlighted the need for further transformation of the South African social welfare system responsible for alcohol and drug treatment service delivery through public–private partnership development and the introduction of a management information system.     

Crime and perceptions after a decade of democracy

Crime has become central to any discussion about the consolidation of democracy in South Africa. Concerns about crime intensified in the years after 1994, as the country attempted to grapple with the apparent ‘crime wave’ that accompanied the transition. A decade later crime is still a priority for government and a concern among citizens, but the clamour that characterised both state and civil society responses in the early years of democracy has receded (See the article by the author in Social Indicators Research 41: 137–168, 1997). This may relate to the decrease in crime levels as reflected by various statistical sources. It is also possible that those whose voices were heard most loudly on the issue – the middle classes – have taken all available measures to protect their property and lives from crime. In all likelihood, South Africans have become accustomed to living in a violent society, and one in which other equally serious problems now require attention. Although the national obsession with crime has waned, the available data nevertheless indicate that the problem still affects many thousands of lives. The impact of crime – in terms of the costs of victimisation, negative perceptions and fear, and the cost of responding to crime – remains high for South African society. This paper considers how crime levels and perceptions about crime and safety have changed over the past decade, and what these trends tell us about the country 10 years into our democracy.     

Surviving the Transition: Trends and Perceptions of Crime in South Africa

Crime and violence have dominated South Africa's transformation over the past two decades. High crime rates cause widespread feelings of insecurity and fear which undermine popular confidence in the democratisation process. Considering both trends and public perceptions, this paper explores changing crime levels over the past decade, elaborating on the problems associated with crime statistics in South Africa, and the salience of the transition for current crime levels. Data is drawn from official police statistics and from victimisation and other surveys. Crime has been increasing gradually in South Africa since 1980. It is, however, since 1990 and not more recently as is popularly believed, that levels have risen sharply. An examination of the statistics shows that despite general increases, not all crimes have been committed with equal frequency and not all areas of the country are similarly affected. These trends are a product of the political transition and are associated with the effects of apartheid and political violence, the breakdown in the criminal justice system and more recently, the growth in organised crime. High crime levels are taking their toll on South Africans. Surveys show that crime rather than socio-economic issues now dominates people's concerns, and that fear of crime is increasing. Currently, fewer people feel safe and believe the government has the situation under control than in previous years. Faced with widespread unemployment on the one hand, and the prospects of development on the other, levels of property crimes will probably continue to increase. While violent crime levels should decline over the medium term, improved relations with the police and a culture of reporting crimes like rape and assault may result in more crime being recorded.     

The utilisation of the bridging technique during therapy to overcome contact-making barriers in adolescents

This article focuses on the utilisation of a bridging technique to overcome contact-making barriers in adolescents. Interruptions or contact boundary disturbances block contact making, as it becomes fixed and prevents the natural and healthy process of organismic self-regulation. A combination of quantitative and qualitative approaches were followed and a single system experimental design, A–B–A–A, was applied in the original study. Qualitative data were collected by means of semi-structured interviews with parents and teachers, and therapeutic intervention with adolescents. Quantitative data were collected from pre- post- and follow-up-intervention assessments, during which the bridging technique was utilised. Fourteen adolescent participants were selected by school teachers and therapists from three different schools, with their parents and teachers: a mainstream school for high-functioning children, a school for children with learning disabilities and a school for children with intellectual disabilities. These adolescents presented behavioural symptoms: aggression, self-mutilation, personal emotional symptoms: depression, suicidal tendencies, as well as contact-making disturbances. The findings indicated that the bridging technique shows potential in working with adolescents to overcome contact-making barriers.