Detection of outliers in high-dimensional data using nu-support vector regression

Support Vector Regression (SVR) is gaining in popularity in the detection of outliers and classification problems in high-dimensional data (HDD) as this technique does not require the data to be of full rank. In real application, most of the data are of high dimensional. Classification of high-dimensional data is needed in applied sciences, in particular, as it is important to discriminate cancerous cells from non-cancerous cells. It is also imperative that outliers are identified before constructing a model on the relationship between the dependent and independent variables to avoid misleading interpretations about the fitting of a model. The standard SVR and the μ-ε-SVR are able to detect outliers; however, they are computationally expensive. The fixed parameters support vector regression (FP-ε-SVR) was put forward to remedy this issue. However, the FP-ε-SVR using ε-SVR is not very successful in identifying outliers. In this article, we propose an alternative method to detect outliers i.e. by employing nu-SVR. The merit of our proposed method is confirmed by three real examples and the Monte Carlo simulation. The results show that our proposed nu-SVR method is very successful in identifying outliers under a variety of situations, and with less computational running time.     

The causes of gender diversity in Malaysian large firms

The issue of women’s representation at the decision-making level in Malaysia has received special attention from the Government since 2004, the year in which it adopted a policy requiring that 30 % of the posts at the decision-making level in the public sector be filled by women. In 2011, the policy was extended to the private sector where 30 % of listed firms’ board seats are to be allocated to women with 2016 being the deadline for compliance. To this end, this paper aims at examining the factors that determine the appointment of women to the boards of Malaysian large firms. Large firms were chosen in this study because they have the resources and the capacity to adopt the policy more readily than smaller firms. The results reveal that gender diversity is positively associated with board size and the presence of family on the board. That is, the larger the board, the more likely it is that women sit on it. The fact that the presence of women on the board is associated with the presence of one or more family members on the board means that the appointment of women to the board is very much influenced by family ties rather than commercial reasons. The results also reveal a positive association between board independence and the proportion of women directors. Further, it is found that board independence is associated positively with the presence of independent women directors. Finally, the results show that firm performance is negatively associated with gender diversity. That is, firms with low financial performance are more likely to have women on their boards. Hence, taken altogether, the evidence suggests that the appointment of women to the board is very much driven by tokenism and family connection rather than by the business case.     

Grocery Perishables Management

In this article, we study the joint pricing and inventory control problem for perishables when a retailer does not sell new and old inventory at the same time. At the beginning of a period, the retailer makes replenishment and pricing decisions, and at the end of a period, the retailer decides whether to dispose of ending inventory or carry it forward to the next period. The objective of the retailer is to maximize the long‐run average profit. Assuming zero lead time, we propose an efficient solution approach to the problem, which is also generalized to solve three extensions to the basic model. A feature of the present study is that we consider explicitly the influence of perishability on the demand. Among the insights gathered from the numerical analysis, we find that dynamic pricing aids extending shelf life and when disposal incurs a lower cost, or even a positive salvage value, the retailer is induced to dispose earlier since the benefit of selling new inventory offsets the loss due to disposal. We also observe that the faster the perceived rate of deterioration, the lower the threshold of the ending inventory for disposal. Perhaps a bit counter‐intuitive, maximizing profits does not mean eliminating disposals or expirations.     

Positive-definite modification of a covariance matrix by minimizing the matrix $$\ell_{\infty}$$ ℓ ∞ norm with applications to portfolio optimization

AStA Advances in Statistical Analysis - The covariance matrix, which should be estimated from the data, plays an important role in many multivariate procedures, and its positive definiteness...     

TEAM INCENTIVES: EVIDENCE FROM A FIRM LEVEL EXPERIMENT

Many organizations rely on teamwork, and yet field evidence on the impacts of team‐based incentives remains scarce. Compared to individual incentives, team incentives can affect productivity by changing both workers’ effort and team composition. We present evidence from a field experiment designed to evaluate the impact of rank incentives and tournaments on the productivity and composition of teams. Strengthening incentives, either through rankings or tournaments, makes workers more likely to form teams with others of similar ability instead of with their friends. Introducing rank incentives however reduces average productivity by 14%, whereas introducing a tournament increases it by 24%. Both effects are heterogeneous: rank incentives only reduce the productivity of teams at the bottom of the productivity distribution, and monetary prize tournaments only increase the productivity of teams at the top. We interpret these results through a theoretical framework that makes precise when the provision of team‐based incentives crowds out the productivity‐enhancing effect of social connections under team production.     

Trade liberalization and industry performance in Bangladesh

This paper analyzes trade liberalization's impact on Bangladesh's manufacturing sector performance. Using firm level input and output data and employing a nonparametric data envelopment analysis (DEA), we calculate technical, pure technical and allocative efficiencies for a sample of 82 firms collected over two periods of time: 1993 and 1998. Then, applying a Malmquist index method, we calculate indices of total factor productivity change and decompose them into technological change, technical efficiency change and scale efficiency change. Our results show that the majority of Bangladeshi manufacturing firms experienced a positive total factor productivity growth between 1993 and 1998, averaging 29% over a five-year period. Export-oriented firms have performed better than import-oriented firms in improving their technical efficiency relative to the best-practice firms in their own sub-group. When these results are compared with the official statistics on the output performance of manufacturing firms, we can conclude that trade liberalization in the 1990s did not adversely affect the Bangladeshi manufacturing industry.     

Psychological Differences Between HIV-Positive Mothers Who Disclose to All, Some, or None of Their Biological Children

This study explored the psychological differences between HIV-positive women who disclosed their serostatus to all, some, or none of their biological children. Data from this project come from a larger, longitudinal investigation of the disclosure process of HIV-infected women. Data were obtained regarding the disclosure processes and the psychological adjustment of women with children ( n  = 90) based on measures of depression, anxiety, and stress. Results suggest that women who disclose to all, some, or none of their children are not significantly different with regard to emotional well-being. Implications for marriage and family therapists are provided.     

Chinese Beliefs in Luck are Linked to Gambling Problems via Strengthened Cognitive Biases: A Mediation Test

Problematic patterns of gambling and their harms are known to have culturally specific expressions. For ethnic Chinese people, patterns of superstitious belief in this community appear to be linked to the elevated rates of gambling-related harms; however, little is known about the mediating psychological mechanisms. To address this issue, we surveyed 333 Chinese gamblers residing internationally and used a mediation analysis to explore how gambling-related cognitive biases, gambling frequency and variety of gambling forms (‘scope’) mediate the association between beliefs in luck and gambling problems. We found that cognitive biases and scope were significant mediators of this link but that the former is a stronger mediator than the latter. The mediating erroneous beliefs were not specific to any particular type of cognitive bias. These results suggest that Chinese beliefs in luck are expressed as gambling cognitive biases that increase the likelihood of gambling problems, and that biases that promote gambling (and its harms) are best understood within their socio-cultural context.