Bayesian covariance matrix estimation using a mixture of decomposable graphical models

We present a Bayesian approach to estimating a covariance matrix by using a prior that is a mixture over all decomposable graphs, with the probability of each graph size specified by the user and graphs of equal size assigned equal probability. Most previous approaches assume that all graphs are equally probable. We show empirically that the prior that assigns equal probability over graph sizes outperforms the prior that assigns equal probability over all graphs in more efficiently estimating the covariance matrix. The prior requires knowing the number of decomposable graphs for each graph size and we give a simulation method for estimating these counts. We also present a Markov chain Monte Carlo method for estimating the posterior distribution of the covariance matrix that is much more efficient than current methods. Both the prior and the simulation method to evaluate the prior apply generally to any decomposable graphical model.     

Ethnic assortative matching in marriage and family outcomes: evidence from the mass migration to the US during 1900–1930

Positive assortative matching in terms of traits such as ethnicity and race has been prevalent in marital formation. One possible explanation for this is that spouses in endogamous marriages possess complementary skills and tastes that increase marital surplus. This paper aims to estimate the effects of ethnic assortative matching on a variety of household outcomes by using the exogenous variation in immigrant flows in the USA during the period 1900–1930 to disentangle the selection effect of partners. The major finding is that the complementarities in home production from same ethnic marriage enhances investment in household public goods such as childrearing and home ownership and reduces the market labor supply of wives. The OLS estimates of the sizes of these effects appear to be substantially biased downward, indicating positive selection into intermarriage in terms of unobservable traits that increase marital surplus.     

A dynamic programming approach of finding an optimal broadcast schedule in minimizing total flow time

We study the problem of (off-line) broadcast scheduling in minimizing total flow time and propose a dynamic programming approach to compute an optimal broadcast schedule. Suppose the broadcast server has k pages and the last page request arrives at time n. The optimal schedule can be computed in O(k³(n+k)^k−1) time for the case that the server has a single broadcast channel. For m channels case, i.e., the server can broadcast m different pages at a time where m < k, the optimal schedule can be computed in O(n^k−m) time when k and m are constants. Note that this broadcast scheduling problem is NP-hard when k is a variable and will take O(n^k−m+1) time when k is fixed and m ≥ 1 with the straightforward implementation of the dynamic programming approach. The preliminary version of this paper appeared in Proceedings of the 11th Annual International Computing and Combinatorics Conference as “Off-line Algorithms for Minimizing the Total Flow Time in Broadcast Scheduling”.     

Frontier Masculinity in the Oil Industry: The Experience of Women Engineers

This study contributes to the empirical evidence in the area of gendered organizations ( Martin and Collinson, 2002 ) and their effects on the women who work in them through an interpretive, ethnographic analysis of the oil industry in Canada, specifically Alberta. The study combines data from interviews with women professionals who have extensive employment experience in the industry, a historical analysis of the industry's development in the area and the personal contextual experience of the author. It is suggested that there are three primary processes which structure the masculinity of the industry: everyday interactions which exclude women; values and beliefs specific to the dominant occupation of engineering which reinforce gender divisions; and a consciousness derived from the powerful symbols of the frontier myth and the romanticized cowboy hero. In this dense cultural web of masculinities, the strategies that the women developed to survive, and, up to a point, to thrive, are double‐edged in that they also reinforced the masculine system, resulting in short‐term individual gains and an apparently long‐term failure to change the masculine values of the industry.     

When, catastrophe happens. Assessment and intervention after sudden traumatic death

The goals of grief after sudden traumatic death is to acknowledge the loss, identify the changes the loss will have in the co-victim's life, and reinvest in life within the new structure. Although these goals seem simple, there is no definitive timeline for when these tasks will be engaged and completed by each of the family members. The pathway and time frame for each co-victim may differ.     

Motivation for ISO 14000 certification: development of a predictive model

Environmental issues have become critical concerns of businesses in recent years. The Singapore Environment Ministry is urging organizations to consider adopting the ISO 14000 Environmental Management Standards. The main purpose of this study was to investigate and identify a number of variables which would be able to predict the motivation of organizations in adopting the ISO 14000 Standards. Through extensive literature search eight possible predictive variables/factors (cost savings, top management concern, employee welfare, meeting environmental regulations, meeting customer expectations, concern over trade barriers, following head office environmental practices, and gaining competitive advantages) were identified. In total, 300 pre-tested survey questionnaires were mailed out to companies from the Electronic and Chemical industries in Singapore. A response rate of about 20% was obtained. The survey instrument was tested for reliability and validity. Using stepwise discriminant analysis, a predictive discriminant function was developed. Only four out of the originally identified eight variables were included in the model. Possible benefits of such a model for Singapore and other industrializing countries are highlighted.     

Attachment to Mothers and Fathers during Middle Childhood: Associations with Child Gender, Grade, and Competence

Attachment relationships of first, third, and fifth graders with their mothers and fathers, and their associations with self‐perceived and teacher‐rated competence, were investigated. Children rated their attachment security with mothers and fathers using the Kerns security scale. Children's perceptions of academic and peer competence were measured using Harter's self‐perception profile, and teachers also rated children's competence. Girls felt greater attachment security to their mothers than to their fathers, and boys felt greater attachment security to their fathers than did girls. Greater attachment security with both mothers and fathers was associated with children's perceptions of greater peer and academic competence, and this association was stronger for older children. A greater sense of attachment security with both parents was associated with greater competence than a sense of attachment security with only one parent. Teacher‐rated competence was significantly related to attachment security with mothers but not fathers.     

Quality of Life of Poor People Living in Remote Areas in Hong Kong

Based on three surveys carried out for studying living conditions of youth, women and elderly living in six remote areas (Tuen Mun, Yuen Long, Tin Shui Wai, Sheung Shui, Fan Ling and Tai Po) in the New Territories of Hong Kong, this paper reports the poverty and social exclusion of these three groups of people. The quality of life of youth, women and elderly is adversely affected by limited job opportunities, high cost of travel for employment, and poor neighbourhoods in the community. However, perceptions of reasons for their problems are different for the three groups, due to differences in bonding and bridging social capital they have, as well as the differences in perceptions on social exclusion and discrimination directed upon them.     

Do Donors Care About the Price of Giving? A Review of the Evidence,with Some Theory to Organise It

VOLUNTAS: International Journal of Voluntary and Nonprofit Organizations - We study how donors decide about which charity to give to. To this end, we construct a theoretical model that clarifies...