The Burr XII System of densities: properties,regression model and applications

We introduce a new class of distributions called the Burr XII system of densities with two extra positive parameters. We provide a comprehensive treatment of some of its mathematical properties. We estimate the model parameters by maximum likelihood. We assess the performance of the maximum likelihood estimators in terms of biases and mean squared errors by means of a simulation study. We also introduce a new family of regression models based on this system of densities. The usefulness of the proposed models is illustrated by means of three real data sets.     

Equivalence testing for similarity in bioassays using bioequivalence criteria on the relative bioactivity

Similarity in bioassays means that the test preparation behaves as a dilution of the standard preparation with respect to their biological effect. Thus, similarity must be investigated to confirm this biological property. Historically, this was typically conducted with traditional hypothesis testing, but this has received substantial criticism. Failing to reject similarity does not imply that the 2 preparations are similar. Also, rejecting similarity when bioassay variability is small might simply demonstrate a nonrelevant deviation in similarity. To remedy these concerns, equivalence testing has been proposed as an alternative to traditional hypothesis testing, and it has found its way in the official guidelines. However, similarity has been discussed mainly in terms of the parameters in the dose‐response curves of the standard and test preparations, but the consequences of nonsimilarity on the relative bioactivity have never been investigated. This article provides a general equivalence approach to evaluate similarity that is directly related to bioequivalence on the relative bioactivity of the standard and test preparations. Bioequivalence on the relative bioactivity can only be guaranteed for positive (only nonblanks) and finite dose intervals. The approach is demonstrated on 4 case studies in which we also show how to calculate a sample size and how to investigate the power of equivalence on similarity.     

The relationship between conflict events and commodity prices in Sudan

Though recent literature uncovers linkages between commodity prices and conflict, the causal direction of the relationship remains ambiguous. We attempt to contribute to this strand of research by studying the dynamic relationship of commodity prices and the onsets of conflict events in Sudan. Using monthly data ranging from January 2001 through December 2012, we identify a structural breakpoint in the multivariate time series model of prices of the three staple foods (sorghum, millet, and wheat) and conflict measure (number of conflict events) in September of 2011. Applying structural vector autoregression (SVAR) and linear non-Gaussian acyclic model (LiNGAM), we find that wheat price fluctuation is a root cause of conflict events in Sudan. We recommend several policy and programmatic suggestions structured toward production, subsidy, price regulation and support for rural farmers and consumers to stabilize commodity prices.     

The negative binomial–beta Weibull regression model to predict the cure of prostate cancer

In this article, for the first time, we propose the negative binomial–beta Weibull (BW) regression model for studying the recurrence of prostate cancer and to predict the cure fraction for patients with clinically localized prostate cancer treated by open radical prostatectomy. The cure model considers that a fraction of the survivors are cured of the disease. The survival function for the population of patients can be modeled by a cure parametric model using the BW distribution. We derive an explicit expansion for the moments of the recurrence time distribution for the uncured individuals. The proposed distribution can be used to model survival data when the hazard rate function is increasing, decreasing, unimodal and bathtub shaped. Another advantage is that the proposed model includes as special sub-models some of the well-known cure rate models discussed in the literature. We derive the appropriate matrices for assessing local influence on the parameter estimates under different perturbation schemes. We analyze a real data set for localized prostate cancer patients after open radical prostatectomy.     

The functional capacity of healthcare workers with history of severe acute respiratory distress syndrome (SARS) complicated with avascular necrosis--case report

Two years after the SARS outbreak in Hong Kong, 128 healthcare workers continued to present with musculoskeletal complaints and 38 workers were diagnosed with avascular necrosis (AVN) in different joints. 13 healthcare workers were referred to six designated Physiotherapy Departments of the Hospital Authority for a tailor-made standardized Functional Capacity Evaluation (FCE) from 2004 to 2005 on a voluntary basis. Job analysis, workers' self-perceived disability and functional capacity, non-material handling tests, and the cardiopulmonary fitness test were performed. Retrospective review of the FCE data showed that there were 17 AVN of hips, 16 AVN of knees, 3 AVN of shoulders. All patients had AVN of lower limb joints. Nearly full ranges of movement (ROM) were observed in the knees involved, but the hip range was decreased for most subjects suffering from hip AVNs. Most workers (n=12) could not complete the cardiopulmonary test due to intolerable joint pain. Six workers' self-perceived physical demands level (PDC) matched with the physical demands level identified by the FCE. 12 healthcare workers attained a sedentary physical demands level and were unable to match with their previous job demands. One staff was classified as light physical demands and managed his original duty. Four workers had returned to work at the time FCE was performed. The tailor-made FCE added information to facilitate the return-to-work planning for the staff. Four more workers returned to work with modified duties one year after the FCE.     

BAYESIAN MODEL SEARCH AND MULTILEVEL INFERENCE FOR SNP ASSOCIATION STUDIES

Technological advances in genotyping have given rise to hypothesis-based association studies of increasing scope. As a result, the scientific hypotheses addressed by these studies have become more complex and more difficult to address using existing analytic methodologies. Obstacles to analysis include inference in the face of multiple comparisons, complications arising from correlations among the SNPs (single nucleotide polymorphisms), choice of their genetic parametrization and missing data. In this paper we present an efficient Bayesian model search strategy that searches over the space of genetic markers and their genetic parametrization. The resulting method for Multilevel Inference of SNP Associations, MISA, allows computation of multilevel posterior probabilities and Bayes factors at the global, gene and SNP level, with the prior distribution on SNP inclusion in the model providing an intrinsic multiplicity correction. We use simulated data sets to characterize MISA's statistical power, and show that MISA has higher power to detect association than standard procedures. Using data from the North Carolina Ovarian Cancer Study (NCOCS), MISA identifies variants that were not identified by standard methods and have been externally "validated" in independent studies. We examine sensitivity of the NCOCS results to prior choice and method for imputing missing data. MISA is available in an R package on CRAN.     

Risks of Mortality and Morbidity from Worldwide Terrorism: 1968–2004

Worldwide data on terrorist incidents between 1968 and 2004 gathered by the RAND Corporation and the Oklahoma City National Memorial Institute for the Prevention of Terrorism (MIPT) were assessed for patterns and trends in morbidity/mortality. Adjusted data analyzed involve a total of 19,828 events, 7,401 "adverse" events (each causing >or= 1 victim), and 86,568 "casualties" (injuries), of which 25,408 were fatal. Most terror-related adverse events, casualties, and deaths involved bombs and guns. Weapon-specific patterns and terror-related risk levels in Israel (IS) have differed markedly from those of all other regions combined (OR). IS had a fatal fraction of casualties about half that of OR, but has experienced relatively constant lifetime terror-related casualty risks on the order of 0.5%--a level 2 to 3 orders of magnitude more than those experienced in OR that increased approximately 100-fold over the same period. Individual event fatality has increased steadily, the median increasing from 14% to 50%. Lorenz curves obtained indicate substantial dispersion among victim/event rates: about half of all victims were caused by the top 2.5% (or 10%) of harm-ranked events in OR (or IS). Extreme values of victim/event rates were approximated fairly well by generalized Pareto models (typically used to fit to data on forest fires, sea levels, earthquakes, etc.). These results were in turn used to forecast maximum OR- and IS-specific victims/event rates through 2080, illustrating empirically-based methods that could be applied to improve strategies to assess, prevent, and manage terror-related risks and consequences.     

Selected Milestones in the Evolution of Career Development Practices in the Twentieth Century

This article briefly chronicles selected major events and personalities that have stimulated and shaped career development practices in the 20th century. In its headings by decades, the article seeks to contextualize major political, social, economic, and scientific themes that have influenced the evolution of models of career behavior, career interventions, and the preparation of counselors to engage in the practice of career development.     

A new useful four-parameter extension of the Gumbel distribution: Properties,regression model and applications using the GAMLSS framework

In this paper we introduce a flexible extension of the Gumbel distribution called the odd log-logistic exponentiated Gumbel distribution. The new model was implemented in GAMLSS package of R software and a brief tutorial on how to use this package is presented throughout the paper. We provide a comprehensive treatment of its general mathematical properties. Further, we propose a new extended regression model considering four regression structures. We discuss estimation methods based on censored and uncensored data. Two simulation studies are presented and four real data sets are applied to illustrating the usefulness of the new model.     

Collaboration,Partnership, Policy,and Practice in Career Development

This article discusses the importance of collaboration among professional organizations, governmental entities, and counselors in behalf of career development. Examples of possible international and national collaborative initiatives and policy emphases are described.