Estimation of gaussian mixtures with rotationally invariant covariance matrices

Homoscedastic and heteroscedastic Gaussian mixtures differ in the constraints placed on the covariance matrices of the mixture components. A new mixture, called herein a strophoscedastic mixture, is defined by a new constraint, This constraint requires the matrices to be identical under orthogonal trans¬formations, where different transformations are allowed for different matrices. It is shown that the M-step of the EM method for estimating the parameters of strophoscedastic mixtures from sample data is explicitly solvable using singular value decompositions. Consequently, the EM-based maximum likelihood estimation algorithm is as easily implemented for strophoscedastic mixtures as it is for homoscedastic and heteroscedastic mixtures. An example of a “noisy” Archimedian spiral is presented.     

Changes in At-Risk American Men's Crime and Substance Use Trajectories Following Fatherhood

Fatherhood can be a turning point in development and in men's crime and substance use trajectories. At-risk boys (N = 206) were assessed annually from ages 12 to 31 years. Crime, arrest, and tobacco, alcohol, and marijuana use trajectories were examined. Marriage was associated with lower levels of crime and less frequent substance use. Following the birth of a first biological child, men's crime trajectories showed slope decreases, and tobacco and alcohol use trajectories showed level decreases. The older men were when they became fathers, the greater the level decreases were in crime and alcohol use and the less the slope decreases were in tobacco and marijuana use. Patterns are consistent with theories of social control and social timetables.     

The Persistence of Neighboring as a Determinant of Community Attachment: A Community Field Perspective*

We examined the community field perspective as a complement to the linear‐development and systemic models of community attachment, wherein community attachment is defined as a social bond to the community of place. We empirically evaluated indicators of the actor's interaction within the social field, such as the perceived quality of neighboring and density of friendships, using social survey and census data from 99 communities in 1994 and 2004 and evaluated as well the percentage change in these indicators from 1994 to 2004. Results show that the community field perspective can complement previous approaches by highlighting the importance of perceived neighboring and friendship density and the persistence of perceived neighboring over time. We suggest implications for community development efforts aimed at enhancing community attachment.     

A study of Bayesian local robustness with applications in actuarial statistics

Local or infinitesimal Bayesian robustness is a powerful tool to study the sensitivity of posterior magnitudes, which cannot be expressed in a simple manner. For these expressions, the global Bayesian robustness methodology does not seem adequate since the practitioner cannot avoid using inappropriate classes of prior distributions in order to make the model mathematically tractable. This situation occurs, for example, when we compute some types of premiums in actuarial statistics in order to fix the premium to be charged to an insurance policy. In this paper, analytical and simple expressions that allow us to study the sensitivity of premiums, which are usually used in automobile insurance are provided by using the local Bayesian robustness methodology. Some examples are examined by using real automobile claim insurance data.     

The Impact of Patronymic Attractiveness on Employability

We link patronymics (first and last names presented together) to success in the job market by investigating the influence of name attractiveness on employability. Using data from a recruitment agency, we tested (binomial regression) for effects associated with age, gender, and name attractiveness on job interview outcomes. We found that candidates with more attractive patronymics were more likely to be retained by employers.     

Double‐mouthed discourse: Interpreting,framing, and participant roles1

In this article I examine multilingual displays in a Congolese Pentecostal church in Cape Town, South Africa. I focus on the simultaneous interpreting of the pastor's French sermon into English. I argue that the interpreting activity performed at church is used as a powerful interactional device to dramatize and shape the pastor's sermon. A close examination of participant roles shows that although these may appear to be predetermined by the interpretee‐interpreter format of the sermon, speaking roles are actually fluid and negotiated. I submit that an important role of the church interpreter is to convey the pastor's inspiration from the Holy Spirit and reach out to the potential audience absent from the here and now of the service. His high emotional engagement helps convey this inspiration prospectively to the audience and retroactively to the pastor himself.