Profile likelihood approaches for semiparametric copula and frailty models for clustered survival data

ABSTRACT

In clustered survival data, the dependence among individual survival times within a cluster has usually been described using copula models and frailty models. In this paper we propose a profile likelihood approach for semiparametric copula models with different cluster sizes. We also propose a likelihood ratio method based on profile likelihood for testing the absence of association parameter (i.e. test of independence) under the copula models, leading to the boundary problem of the parameter space. For this purpose, we show via simulation study that the proposed likelihood ratio method using an asymptotic chi-square mixture distribution performs well as sample size increases. We compare the behaviors of the two models using the profile likelihood approach under a semiparametric setting. The proposed method is demonstrated using two well-known data sets.     

Are they ideological renegades? Fathers' experiences on taking parental leave and gender dynamics in Korea: A qualitative study

Despite their fear of repercussions on career advancement and gender identity, Korean fathers taking parental leave have continually increased. Why do Korean fathers take parental leave in spite of the risk of being stigmatized as less masculine and less ideal workers? Are they willing to be ‘ideological renegades' to be new involved fathers? In‐depth interviews with fathers who took parental leave provide interesting answers. Overall, taking parental leave does not make fathers become ideological renegades since it is mainly utilized in a manner that accommodates the work devotion schema, deviating from the formal policy objectives. This deviant utilization is encouraged and even valued by organizations. This may be part of a psychological contract between organizations and employees, ensuring that employees are dedicated to their career even during parental leave. Furthermore, beyond the legal eligibility of uptake, informal but powerful ‘organizational eligibility' such as high performance or their contribution to the organization, makes not only the likelihood but also the aftermath of taking up different across fathers. As a result, a hierarchy among fathers with class connotations emerges. This hierarchy among fathers, combined with the traditional gender hierarchy, may reinforce the masculine fabric of ideal workers as the norm.     

Bursting With Laughter

Celio Ferreira. Palauan cosmology: dominance in a traditional Micronesian society (Gothenburg Studies in Social Anthropology 11). Göteborg: Acta Universitatis Gothoburgensis. 1987. vi, 300 pp., figures, plates, glossary, references. SEK 200 (paper) ISBN 91 7346 183 0 ISSN 0348 4076.

Richard J. Parmentier. The sacred remains: myth, history and polity in Belau. Chicago: The University of Chicago Press. 1987. xxiii, 309pp., figures, maps, photographs, tables, glossary, place names, references, index. ISBN 0 226 64695 5 (hardcover) ISBN 0 226 64696 3 (paper).     

Annual Review: Practice and Research in Career Counseling and Development—1998

The article reviews the practice and research literature in career counseling and development in 1998. The literature is presented and discussed under the following topical headings: contexts and populations, career processes, transitions, career assessment, and career counseling, services and programs.     

Bayesian Interval Estimation for the Difference in TPRs and FPRs of Two Diagnostic Tests with Unverified Negatives

We derive Bayesian interval estimators for the differences in the true positive rates and false positive rates of two dichotomous diagnostic tests applied to the members of two distinct populations. The populations have varying disease prevalences with unverified negatives. We compare the performance of the Bayesian credible interval to the Wald interval using Monte Carlo simulation for a spectrum of different TPRs, FPRs, and sample sizes. For the case of a low TPR and low FPR, we found that a Bayesian credible interval with relatively noninformative priors performed well. We obtain similar interval comparison results for the cases of a high TPR and high FPR, a high TPR and low FPR, and of a high TPR and mixed FPR after incorporating mildly informative priors.     

Bayesian mixture models for complex high dimensional count data in phage display experiments

Summary.  Phage display is a biological process that is used to screen random peptide libraries for ligands that bind to a target of interest with high affinity. On the basis of a count data set from an innovative multistage phage display experiment, we propose a class of Bayesian mixture models to cluster peptide counts into three groups that exhibit different display patterns across stages. Among the three groups, the investigators are particularly interested in that with an ascending display pattern in the counts, which implies that the peptides are likely to bind to the target with strong affinity. We apply a Bayesian false discovery rate approach to identify the peptides with the strongest affinity within the group. A list of peptides is obtained, among which important ones with meaningful functions are further validated by biologists. To examine the performance of the Bayesian model, we conduct a simulation study and obtain desirable results.