A Matrix Variate Closed Skew-Normal Distribution with Applications to Stochastic Frontier Analysis

In this article, we introduce the matrix extension of the closed skew-normal distribution and give two constructions for it: a marginal one and another based on hidden truncation. Important basic properties of the distribution are presented such as its closure under linear transformation and moment generating function. We also give distributional results for quadratic forms involving random matrices distributed according to two particular cases of it. Using an additive construction, we derive a submodel which can be employed to describe the compound error structure of a very general multivariate stochastic frontier model. Finally, we consider the skew-elliptical extension of the proposed distribution.     

A Bayes comparison of Weibull extension and modified Weibull models for data showing bathtub hazard rate

A number of models have been proposed in the literature to model data reflecting bathtub-shaped hazard rate functions. Mixture distributions provide the obvious choice for modelling such data sets but these contain too many parameters and hamper the accuracy of the inferential procedures particularly when the data are meagre. Recently, a few distributions have been proposed which are simply generalizations of the two-parameter Weibull model and are capable of producing bathtub behaviour of the hazard rate function. The Weibull extension and the modified Weibull models are two such families. This study focuses on comparing these two distributions for data sets exhibiting bathtub shape of the hazard rate. Bayesian tools are preferred due to their wide range of applicability in various nested and non-nested model comparison problems. Real data illustrations are provided so that a particular model can be recommended based on various tools of model comparison discussed in the paper.     

On the type-B integral equation and the distribution of wilks statist for testing independence of several groups of variables

In this paper, WILKS'type-B integral equation is solved in the general form of a series of beta functions and a series of weighted gamma functions as proposed by WALD and BROOKNER 1941. The coefficients in both representations can be obtained by explicit recurrence relartions, therefore the results solve many distributional problems and have the fewest computational difficulties of any representation that has surfaced to date. The radius of convergence of the second series representation is given, whereas the convergence property of the first series representation is given, whereas the convergence property of the first series representation was studied by WALD and Brookner. The exact null distributions of WILKS' statistic A for testing the independence of several groups of variables and of V = -log A are given. The coefficients in all the series representration can be computed recursilvely and hence can be obtained easily with the help of modern computatinal facilities     

Online Control Charts for Process Averages Based on Repeated Median Filters

Two types of estimates of process level, namely repeated median estimates (Siegel, 1982 Siegel , A. F. ( 1982 ). Robust regression using repeated medians . Biometrika 69 : 242 – 244 .[Crossref], [Web of Science ®] , [Google Scholar]) and full online estimates (Gather et al., 2006 Gather , U. , Schettlinger , K. , Fried , R. ( 2006 ). Online signal extraction by robust linear regression . Computational Statistics 21 : 33 – 51 .[Crossref], [Web of Science ®] , [Google Scholar]) based on repeated median filters, are used to develop control charts. The distributional properties of the estimates are studied using simulation and these are found to closely follow normal distribution. The repeated median being robust against outliers with asymptotically 50% breakdown value and having small standard deviation is found to be useful as a basis for monitoring process averages. The control charts using repeated median estimates have been recommended for general use.     

Citing history

ABSTRACT

Although rarely considered within the existing scholarship on social movements, even a cursory analysis of protest activity suggests that movements regularly invoke historical citations (whether consciously or not) while working to clarify aims and mobilize constituencies. In order to make sense of this process, and to account for the variations that arise among the different citation modalities favored by movements on opposite ends of the political spectrum, I draw upon the theoretical contributions of Marxist cultural critic Walter Benjamin and, in particular, on his exploration of ‘wish images’ and ‘dialectical images,’ their attributes, and their interrelationship. According to Benjamin, such images summoned the past either to project visions of future happiness (as with the wish image) or to deposit the witness before a moment of decisive, present-tense reckoning. After outlining the role of historical citation in social movements and in the broader cultural field through which these movements find expression, I analyze two recent protest events – the ‘Unite the Right’ rally in Charlottesville, VA, in which wish images were actively deployed, and the 2017 Women’s Strike in New York City, where a dialectical image arose from the constellated nodes of the march’s route – to consider the relationship between citation modality and protest outcome. Following from this analysis, and in keeping with the unapologetically partisan nature of my investigation, I conclude by advancing some strategic recommendations for movements seeking – as Benjamin once enjoined – to ‘improve our position in the struggle against Fascism.’     

Adolescent Gambling Behavior: A Prevalence Study and Examination of the Correlates Associated with Problem Gambling

Eight-hundred and seventeen adolescent high school students in the Montreal region completed the DSM-IV-J gambling screen along with a questionnaire devised by the authors inquiring about their gambling behavior, including items assessing the types of activities in which they engage, frequency of involvement, reasons for gambling, and their cognitive perceptions of gambling activities. The results indicate that, in general, 80.2% of students reported having gambled during the previous year, with 35.1% gambling a minimum of once per week. Adolescents reported participating in gambling behavior more often than any other addictive behavior, including cigarette smoking, alcohol consumption, and illicit drug use. The mean age of onset of gambling behavior for the sample was 11.5 years. The rate of pathological gambling was 4.7% as measured by the DSM-IV-J. Pathological gamblers were more likely to have parents with gambling problems and to be engaging in illegal activities than non-pathological gamblers. Gender differences were evident, with males engaging in gambling activities more than females. Differences in game preferences were found, with males more attracted to sports lottery tickets and sports pool betting and females more attracted to lottery tickets and bingo. Gambling awareness and prevention issues are addressed.     

Dating and friendships in adolescence: Variation across same-sex and other-sex romantic partners

This research examined associations between dating and number of friends for rural adolescents with same-sex and other-sex dating partners using longitudinal sociometric data (N = 2826; 55% female, 87% White, mean age = 14 at baseline). In multilevel models assessing within-person change, boys gained female friends when they were in same-sex romantic relationships, compared to when they were single. In contrast, girls in same-sex relationships lost female friends and gained male friends. Adolescents in other-sex romantic relationships gained same-sex friends compared to when they were single. Results advance understanding of adolescent social and sexual development, suggesting that sexual minority adolescents find allies when dating but may struggle to maintain same-sex friendships.     

On some mixture models based on the Birnbaum-Saunders distribution and associated inference

In this paper, we consider three different mixture models based on the Birnbaum-Saunders (BS) distribution, viz., (1) mixture of two different BS distributions, (2) mixture of a BS distribution and a length-biased version of another BS distribution, and (3) mixture of a BS distribution and its length-biased version. For all these models, we study their characteristics including the shape of their density and hazard rate functions. For the maximum likelihood estimation of the model parameters, we use the EM algorithm. For the purpose of illustration, we analyze two data sets related to enzyme and depressive condition problems. In the case of the enzyme data, it is shown that Model 1 provides the best fit, while for the depressive condition data, it is shown all three models fit well with Model 3 providing the best fit.     

DISTRIBUTION-FREE TESTS BASED ON SUB-SAMPLE EXTREMA FOR TESTING AGAINST POSITIVE DEPENDENCE

A class of distribution-free tests based on U-statistics has been proposed for testing the null hypothesis of independence against positive quadrant dependence. The tests are based on U-statistics and the Kendall's-tau test belongs to this class.