A superiority problem in misspecified restricted linear models

Abstract

In this article we study the relationship between principal component analysis and a multivariate dependency measure. It is shown, via simulated examples and real data, that the information provided by principal components is compatible with that obtained via the dependency measure δ. Furthermore, we show that in some instances in which principal component analysis fails to give reasonable results due to nonlinearity among the random variables, the dependency statistic δ still provides good results. Finally, we give some ideas about using the statistic δ in order to reduce the dimensionality of a given data set.     

Robust estimation of the correlation matrix of longitudinal data

We propose a double-robust procedure for modeling the correlation matrix of a longitudinal dataset. It is based on an alternative Cholesky decomposition of the form Σ=DLL ^? D where D is a diagonal matrix proportional to the square roots of the diagonal entries of Σ and L is a unit lower-triangular matrix determining solely the correlation matrix. The first robustness is with respect to model misspecification for the innovation variances in D, and the second is robustness to outliers in the data. The latter is handled using heavy-tailed multivariate t-distributions with unknown degrees of freedom. We develop a Fisher scoring algorithm for computing the maximum likelihood estimator of the parameters when the nonredundant and unconstrained entries of (L,D) are modeled parsimoniously using covariates. We compare our results with those based on the modified Cholesky decomposition of the form LD ² L ^? using simulations and a real dataset.     

An investigation of mental health and personality in Swedish social work students upon entry to university training

The aims were to describe Swedish social work students' personality characteristics upon entry to their training and to analyze relationships between personality traits, mental health, and some sociodemographic variables. One hundred and twenty-one female social work students completed a sociodemographic form, the Temperament and Character Inventory, and the Symptom Checklist. They scored significantly higher on harm avoidance, reward dependence, and self-transcendence and reported more somatization, obsessive compulsive, and phobic-anxious symptoms, and less hostility, than Swedish individuals from the general population of the same age. Personality traits significantly predicted the various mental symptom scores. It is recommended to implement modules or training courses within social work training in Sweden that bring an improvement of self-directedness and cooperativeness character trait into focus.     

YOUTH,REVOLUTION, AND REPRESSION

We develop a simple model to study the effect of age structure on the interactions between the state and dissidents. Younger populations are more prone to protest. As the population grows younger, states that can discriminately target repression to different groups, but cannot concede discriminately, decrease repression. In contrast, states that can target concession, but not repression, increase repression. We test these results in nonmilitary single‐party regimes and military regimes without political parties. Moreover, we study state response to dissent in East European communist regimes in the late 1980s, showing that state response was more repressive in countries with younger populations. (JEL D74)     

HIV prevention barriers in transgender women: a qualitative study

Abstract

Sexual contact is still one of the most important routes of HIV transmission. The aim of this study was identify the factors that underlie the higher prevalence of high-risk sexual behaviors in a sample of transgender women in Iran. The qualitative study used face-to-face, semi-structured, in-depth interviews in a sample of 15 transgender women. Our participants used sexual practices as a way to be approved/accepted as a woman. Using sex for this purpose led them to engage in high-risk sexual relationships. It is essential to consider these issues in consulting and education about high-risk behaviors.     

A faster strongly polynomial time algorithm to solve the minimum cost tension problem

This paper presents a strongly polynomial time algorithm for the minimum cost tension problem, which runs in \(O(\max \{m^3n, m^2 \log n(m+n \log n)\})\) time, where n and m denote the number of nodes and number of arcs, respectively. Our algorithm improves upon the previous strongly polynomial time of \(O(n^4 m^3 \log n)\) due to Hadjiat and Maurras (Discret Math 165(166):377–394, 1997).     

Reproducibility of the Dose-Response Curve of Steroid-Induced Cleft Palate in Mice

Pregnant CD-1 mice were exposed to cortisone acetate at doses ranging from 20 to 100 mg/kg/ day on days 10-13 by oral and intramuscular routes. Multiple replicate assays were conducted under identical conditions to assess the reproducibility of the dose–response curve for cleft palate. The data were fitted to the probit, logistic, multistage or Armitage-Doll, and Weibull dose-response model separately for each route of exposure. The curves were then tested for parallel slopes (probit and logistic models) or coincidence of model parameters (multistage and Weibull models). The 19 replicate experiments had a wide range of slope estimates, wider for the oral than for the intramuscular experiments. For all models and both routes of exposure the null hypothesis of equality of slopes was rejected at a significant level of p < 0.001. For the intramuscular group of replicates, rejection of slope equality could in part be explained by not maintaining a standard dosing regime. The rejection of equivalence of dose-response curves from replicate studies showed that it is difficult to reproduce dose-response data of a single study within the limits defined by the dose-response model. This has important consequences for quantitative risk assessment, public health measures, or development of mechanistic theories which are typically based on a single animal bioassay.     

Workplace discrimination and diabetes: the EEOC Americans with Disabilities Act research project

Using the Integrated Mission System of the Equal Employment Opportunity Commission, the employment discrimination experience of Americans with diabetes is documented. Researchers compare and contrast the key dimensions of workplace discrimination involving Americans with diabetes and persons with other physical, sensory, and neurological impairments. Specifically, the researchers examine demographic characteristics of the charging parties; the industry designation, location, and size of employers against whom complaints are filed; the nature of discrimination (i.e., type of adverse action) alleged to occur; and the legal outcome or resolution of these complaints. Findings indicate that persons with diabetes were more likely to encounter discrimination involving discharge, constructive discharge, discipline and suspension - all job retention issues. Persons with diabetes were less likely to encounter discrimination involving hiring, reasonable accommodation, non-pension benefits, and layoff. They were also more likely to encounter discrimination when they were older or from specific ethnic backgrounds, or when they worked for small employers or in the Southern United States. Implications for policy and advocacy are addressed.     

Finding a contra-risk path between two nodes in undirected graphs

Given an undirected graph with a source node s and a sink node t. The anti-risk path problem is defined as the problem of finding a path between node s to node t with the least risk under the assumption that at most one edge of each path may be blocked. Xiao et al. (J Comb Optim 17:235–246, 2009) defined the problem and presented an \(O(mn+n^2 \log n)\) time algorithm to find an anti-risk path, where n and m are the number of nodes and edges, respectively. Recently, Mahadeokar and Saxena (J Comb Optim 27:798–807, 2014) solved the problem in \(O(m+n \log n)\) time. In this paper, first, a new version of the anti-risk path (called contra-risk path) is defined, which is more effective than an anti-risk path in many networks. Then, an algorithm to find a contra-risk path is presented, which runs in \(O(m+n \log n)\) time.