Properties of the bridge sampler with a focus on splitting the MCMC sample

Computation of normalizing constants is a fundamental mathematical problem in various disciplines, particularly in Bayesian model selection problems. A sampling-based technique known as bridge sampling (Meng and Wong in Stat Sin 6(4):831–860, 1996) has been found to produce accurate estimates of normalizing constants and is shown to possess good asymptotic properties. For small to moderate sample sizes (as in situations with limited computational resources), we demonstrate that the (optimal) bridge sampler produces biased estimates. Specifically, when one density (we denote as $$p_2$$) is constructed to be close to the target density (we denote as $$p_1$$) using method of moments, our simulation-based results indicate that the correlation-induced bias through the moment-matching procedure is non-negligible. More crucially, the bias amplifies as the dimensionality of the problem increases. Thus, a series of theoretical as well as empirical investigations is carried out to identify the nature and origin of the bias. We then examine the effect of sample size allocation on the accuracy of bridge sampling estimates and discovered that one possibility of reducing both the bias and standard error with a small increase in computational effort is by drawing extra samples from the moment-matched density $$p_2$$ (which we assume easy to sample from), provided that the evaluation of $$p_1$$ is not too expensive. We proceed to show how the simple adaptive approach we termed “splitting” manages to alleviate the correlation-induced bias at the expense of a higher standard error, irrespective of the dimensionality involved. We also slightly modified the strategy suggested by Wang et al. (Warp bridge sampling: the next generation, Preprint, 2019. arXiv:1609.07690) to address the issue of the increase in standard error due to splitting, which is later generalized to further improve the efficiency. We conclude the paper by offering our insights of the application of a combination of these adaptive methods to improve the accuracy of bridge sampling estimates in Bayesian applications (where posterior samples are typically expensive to generate) based on the preceding investigations, with an application to a practical example.     

Sex Differences in Perceived Family Functioning and Family Resources in Hong Kong Families: Implications for Social Work Practice

Although enhancing family functioning has become a rising concern of social workers in Chinese contexts such as Hong Kong, little has been known on perceived family functioning and family resources. To fill in this knowledge gap, this article reports part of the results of a telephone survey conducted in Hong Kong, aiming to identify the sex differences in these two areas. The results of the study have shown that Chinese women perceived better affective involvement, one of the crucial indicators of family functioning, than Chinese men. However, among the different family resources, men rated better physical and mental well-being whereas women's social connection was stronger than men's. Further analysis have shown that the linkage of three family resources (namely stress coping efficacy, time spent with family and income) to perceived family functioning was statistically significant irrespective of genders. Implications of this study for social work practice are discussed at the end of the article.     

Welfare attitudes and social class: the case of Hong Kong in comparative perspective

Based on a survey of Hong Kong residents, this article explores the attitudes towards the welfare state and whether or not there are significant differences between different social classes with regard to their approval of the welfare state. The findings were then compared with those for Sweden and the USA. The study shows that Hong Kong residents strongly approve of the welfare state. The strength of their support is similar to that in Sweden and is far stronger than in the USA. In Hong Kong, the influence of social class on attitudes towards the welfare state is negligible. In some cases, the privileged classes expressed greater approval for the welfare state than the underprivileged classes. This is in striking contrast to the experiences in Sweden and the USA where the underprivileged classes are more supportive of the welfare state than are the privileged classes.     

Pretrial Predictors of Judgments in the O. J. Simpson Case

Five hundred seventy-eight community college and four-year state university students responded to questionnaires designed to assess judgments regarding O. J. Simpson's guilt, beliefs surrounding the case, general attitudes, and background information. Although African Americans were more likely to perceive Simpson as innocent than non–African Americans, correlation analyses revealed that, for the most part, the same predictors explained African Americans' and non–African American's judgments of guilt. Finally, set-wise hierarchical regression analyses indicated that case-related beliefs that Simpson abused Nicole Brown Simpson and that the system was biased against him accounted for more significant incremental variance than did demographic variables such as age and ethnicity, personal experiences, and general attitudes. The results suggested that the racial polarization emphasized in public polls does not reflect the diversity of beliefs that existed within both African American and European American populations.     

Interprofessional collaboration between social workers and school counsellors in tackling youth at-risk behaviour

In Singapore, although youths are engaged in school, at-risk behaviours still prevail. This study discovers the experiences of collaboration between social workers and school counsellors when working together to tackle the multi-dimensional problems that youths face. It is posited that the collaborative processes have strengthened as seen in the role clarity, flexibility and tight communicative processes amongst professionals. There are also issues of concerns raised, such as confidentiality and clashes in agenda. These are discussed in light of the processes and orientations that influenced professionals in their practise. Last, relevant recommendations are given to develop collaborative work.     

Mission Possible; Building Social Work Professional Identity through Fieldwork Placements in China

Social work training programmes in China have increased rapidly in the last decade. Their growth mirrors the increase in social problems that China faces as its economy develops and the disparities between rich and poor multiply. There is little recognition either by the government or citizens of the profession of social work and so no clear idea of what it might achieve. Thus the development of social work in China faces many difficulties among which is a dearth of professionally qualified social workers to teach, and to supervise fieldwork placements. This paper discusses a collaborative MSW programme between the University of Hong Kong and Fudan University in Shanghai. It analyses the growth in professional identity of nine students in the programme undertaking their first supervised fieldwork placement in Shanghai. They were asked to write 500‐word statements before and after their placement about their understanding of the role of social workers and their sense of professional identity. An analysis of these statements forms the basis of this article. The article addresses the issue of whether the construction of a professional identity will rest with members of the embryonic profession or with government bureaucrats largely concerned with the maintenance of stability and the management of social change.     

Evaluating a Measure of ‘Social Orientation’ of Chinese Students in Social Work: Developing its Reliability and Validity

This study examines the reliability and validity of a measure of ‘social orientation’ indigenously developed from Chinese students of social work in Hong Kong. By administering two tests with Chinese social work students (n = 293 and n = 304) at associate degree level, the measure achieves strong internal consistency with r>0.75 and test–retest consistency with r>0.63. The instrument also has strong validity by attempting factor analysis of items generated from qualitative data in in‐depth interviews. The development of this indigenous measure of ‘social orientation’ will contribute to an understanding of the authoritarian, relationship and ‘other’ orientation of Chinese social work students. The authors propose that this will be a crucial factor in influencing the response of Chinese students towards different teaching and learning approaches in social work education.     

Predicting help-seeking behavior: The impact of knowing someone close who has sought help

ABSTRACT

Objectives: This study sought to replicate and extend research on social facilitators of college student's help seeking for psychological problems. Participants: We collected data on 420 ethnically diverse college students at a large public university (September 2008–May 2010). Methods: Students completed a cross-sectional online survey. Results: We found that students who were aware of close others' (eg, family, friends) help seeking were two times more likely to have sought formal (eg, psychologist) and informal (eg, clergy) help themselves. Tests of moderation revealed the incremental effect (ie, controlling for help-seeking attitudes, internalizing symptoms, cultural demographics) of close others' formal help seeking was strong and significant for men (R² = 0.112), while it was negligible and nonsignificant for women (R² = .002). Conclusions: We discuss the importance for students—particularly men—to learn about close others' help seeking for facilitating their own help seeking during times of distress.     

Disparities Between HIV Testing Levels and the Self-Reported HIV-Negative Status of Sexually Active College Students

The methodological issues of using self-reported human immunodeficiency virus (HIV) testing history to determine HIV infection status are understudied. This study aimed to assess the disparities between HIV testing history and self-reported HIV status, with a specific objective of estimating the prevalence of self-reported HIV-negative status in sexually active students who had never had an HIV test (inaccurate self-disclosure). Participants were recruited from four Hong Kong universities; 255 students were included in the analysis, with 16.1% of participants being men who have sex with men (MSM). Overall, 81.6% of participants reported they never had been tested for HIV, with inaccurate self-disclosure by 65.9% of participants. Among participants who used condoms inconsistently, only 20.2% had had HIV tests, with inaccurate self-disclosure by 66.7% of subjects. Among MSM students, only 36.6% had had HIV tests, with inaccurate self-disclosure by 61.0% of participants. Among MSM students who used condoms inconsistently, only 35.1% had had HIV tests, with inaccurate self-disclosure by 62.2% of participants. The findings raise concerns about the use of self-reported HIV status in clinical practice and research. The low prevalence of HIV testing found suggests that interventions to promote HIV testing should be continued.     

Examining Gender Differences for Gambling Engagement and Gambling Problems Among Emerging Adults

Gambling is fast becoming a public health problem in the United States, especially among emerging adults (18–25 year olds). Since 1995, rates have recently doubled with around 7–11 % of the emerging adult population having problems with gambling (Shaffer et al. in Am J Public Health 89(9):1369–1376, 1999; Cyders and Smith in Pers Individ Diff 45(6):503–508, 2008). Some states have lowered their gambling age to 18 years old; in turn, the gambling industry has recently oriented their market to target this younger population. However, little is known about the gender variation and the factors placing emerging adults at risk for getting engaged and developing problems with gambling. The purpose of the study was to determine the risk factors accounting for gender differences at the two levels of gambling involvement: engagement and problems. Mediation analyses revealed that impulsive coping and risk-taking were significant partial mediators for gender differences on engagement in gambling. Men took more risks and had lower levels of impulsive coping than women, and those who took more risks and had lower levels of impulsive coping were more likely to engage in gambling. Risk-taking and social anxiety were the significant mediators for gender differences in problems with gambling. Men took more risks and were more socially anxious than women, and greater risk-taking and more socially anxious individuals tended to have more problems with gambling. Implications for counseling preventions and intervention strategies are discussed.