When Costs Are Unequal and Unknown: A Subtree Grafting Approach for Unbalanced Data Classification*

In binary classifications, a decision tree learned from unbalanced data typically creates an important challenge related to the high misclassification rate of the minority class. Assigning different misclassification costs can address this problem, though usually at the cost of accuracy for the majority class. This effect can be particularly hazardous if the costs cannot be specified precisely. When the costs are unknown or difficult to determine, decision makers may prefer a classifier with more balanced accuracy for both classes rather than a standard or cost‐sensitively learned one. In the context of learning trees, this research therefore proposes a new tree induction approach called subtree grafting (STG). On the basis of a real bank data set and several other data sets, we test the proposed STG method and find that our proposed approach provides a successful compromise between standard and cost‐sensitive trees.     

The Impact of Family Transitions on Child Fostering in Rural Malawi

Despite the frequency of divorce and remarriage across much of sub-Saharan Africa, little is known about what these events mean for the living arrangements of children. We use longitudinal data from rural Malawi to examine the effects of family transitions on the prevalence and incidence of child fostering, or children residing apart from their living parents. We find that between 7 % and 15 % of children aged 3–14 are out-fostered over the two-year intersurvey period. Although divorce appears to be a significant driver of child fostering in the cross-sectional analysis, it is not significantly associated with the incidence of out-fostering. In contrast, maternal remarriage has both a lagged and an immediate effect on the incidence of out-fostering. Furthermore, the likelihood of out-fostering is even higher among children whose mother remarried and had a new child during the intersurvey period. Using longitudinal data collected from living mothers rather than from children’s current foster homes offers new insights into the reasons children are sent to live with others besides their parents.     

Learning in the Allais paradox

Whereas both the Allais paradox, the first empirical challenge of the classical rationality assumptions, and learning have been the focus of many experimental investigations, no experimental study exists today into learning in the pure context of the Allais paradox. This paper presents such a study. We find that choices converge to expected utility maximization if subjects are given the opportunity to learn by both thought and experience, but less so when they learn by thought only. To the extent that genuine preferences should be measured with proper learning and incentives, our study gives the first pure demonstration that irrationalities such as in the Allais paradox are less pronounced than often thought. Paul Anand and Stefan Trautmann made helpful comments.     

Experiences of rural male caregivers of older adults with their informal support networks

More male caregivers are assuming primary caregiving roles for older adults with chronic health conditions. One of the main sources of support for many caregivers is the assistance that is provided by members of their informal support network. Little is known about the relationship between male caregivers and their informal support networks. This qualitative study examines the experience of male caregivers with their informal support networks, specifically looking at two phenomena: (1) Perceptions of the male caregivers about the willingness of their informal support networks to provide caregiving assistance and (2) Willingness of the male caregivers to ask their informal support networks for assistance. Twenty male caregivers were recruited across a rural Midwestern state. Each male caregiver engaged in two interviews that lasted between 60 and 120 minutes. Seven themes emerged from the data about the male caregivers experience with their informal support networks. Results from this study have implications for geriatric health professionals who work with male caregivers to obtain the necessary amount of caregiving assistance.     

Internet Paradox Revisited

Kraut et al. (1998) reported negative effects of using the Internet on social involvement and psychological well-being among new Internet users in 1995–96. We called the effects a "paradox" because participants used the Internet heavily for communication, which generally has positive effects. A 3-year follow-up of 208 of these respondents found that negative effects dissipated. We also report findings from a longitudinal survey in 1998–99 of 406 new computer and television purchasers. This sample generally experienced positive effects of using the Internet on communication, social involvement, and well-being. However, consistent with a "rich get richer" model, using the Internet predicted better outcomes for extraverts and those with more social support but worse outcomes for introverts and those with less support.     

Collective Emotions in Conflict Situations: Societal Implications

It is well established today that emotions are an important part of most societal dynamics. The current article focuses on the role of different collective emotional elements in creating, preserving, and resolving conflicts. The main premise is that collective emotions play a pivotal role in shaping individual and societal responses to conflicting events and in contributing to the evolvement of a social context that maintains the emotional climate and collective emotional orientation that have developed. The first part of the article provides a conceptual framework to discuss the relations between conflict, context, and collective emotions. The second part uses the conceptual framework to discuss the societal implications of the articles presented in this issue. Taken together, the parts create a platform for future research on the role of collective emotions in conflict resolution and the construction of cultures of peace.     

On the Trail of a Radical Pedagogy for Social Work Education

Correspondence to Dr William De Maria, Department of Social Work and Social Policy, The University of Queensland, Brisbane 4072, Australia. Summary This article uses a general decade by decade approach to notethe emergence (1970s), decline (1980s), and re-emergence (1990s)of radical social work. An issue for this 1990s'-type radicalsocial work will become one of attending to its own teachingmission. A range of radical pedagogic principles is presented:cause-sensitive action, tailoring, contradiction-based learning,de-monopolized values, radical analysis, polemic storytelling,and centring marginality.     

The Meaning of Trust for Brazilians with Higher Education

The validity of the World Values Survey (WVS) question used to measure trust is disputed over and this article is intended to present the results of an online survey, conducted in Brazil, which tested the meaning of the term trust in the WVS question. The surveyed population is entirely Brazilian and the majority has received some form of higher education. The results of the survey partially corroborate the validity of the WVS and partially deny it. Within the results of this survey there are predominantly two dominant perspectives represented within the surveyed population including: respondents who think in friends and relatives as part of most people have a higher probability of also saying to trust most people which means that different people may be answering slightly different questions. However, respondents who say that trust most people have higher levels of trust in people in general than in family if compared with respondents who say to not trust most people which is in accordance with the expectation that the question adequately measures generalized interpersonal trust.