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Conformal mapping for multivariate Cauchy families  [PDF]
Shogo Kato,Peter McCullagh
Statistics , 2015,
Abstract: We discuss some statistical properties of the multivariate Cauchy families on the Euclidean space and on the sphere. It is seen that the two multivariate Cauchy families are closed under conformal mapping called the M\"obius transformation and that, for each Cauchy family, there is a similar induced transformation on the parameter space. Some properties of a marginal distribution of the spherical Cauchy such as certain moments and a closure property associated with the real M\"obius group are obtained. It is shown that the two multivariate Cauchy families are connected via stereographic projection. Maximum likelihood estimation for the two Cauchy families is considered; closed-form expressions for the maximum likelihood estimators are available when the sample size is not greater than three, and the unimodality holds for the maximized likelihood functions. A Kent-type extension of the spherical Cauchy arising from an extended M\"obius subgroup is briefly considered.
Multivariate Evolutionary Analyses in Astrophysics  [PDF]
Didier Fraix-Burnet
Statistics , 2011,
Abstract: The large amount of data on galaxies, up to higher and higher redshifts, asks for sophisticated statistical approaches to build adequate classifications. Multivariate cluster analyses, that compare objects for their global similarities, are still confidential in astrophysics, probably because their results are somewhat difficult to interpret. We believe that the missing key is the unavoidable characteristics in our Universe: evolution. Our approach, known as Astrocladistics, is based on the evolutionary nature of both galaxies and their properties. It gathers objects according to their "histories" and establishes an evolutionary scenario among groups of objects. In this presentation, I show two recent results on globular clusters and earlytype galaxies to illustrate how the evolutionary concepts of Astrocladistics can also be useful for multivariate analyses such as K-means Cluster Analysis.
Double Dose: High Family Conflict Enhances the Effect of Media Violence Exposure on Adolescents’ Aggression  [PDF]
Karin M. Fikkers,Jessica Taylor Piotrowski,Wouter D. Weeda,Helen G. M. Vossen,Patti M. Valkenburg
Societies , 2013, DOI: 10.3390/soc3030280
Abstract: We investigated how exposure to media violence and family conflict affects adolescents’ subsequent aggressive behavior. We expected a double dose effect, meaning that high media violence exposure would lead to higher levels of aggression for adolescents in high conflict families compared to low conflict families. A total of 499 adolescents (aged 10 to 14, 48% girls) participated in a two-wave longitudinal survey (4-month interval). Survey questions assessed their exposure to violence on television and in electronic games, family conflict, and aggressive behavior. Analyses revealed a significant interaction between media violence and family conflict. In families with higher conflict, higher media violence exposure was related to increased subsequent aggression. This study is the first to show a double dose effect of media violence and family conflict on adolescents’ aggression. These findings underscore the important role of the family in shaping the effects of adolescents’ media use on their social development.
The Effects of Parenting Styles and Temperament on Adolescent Aggression: Examining Unique, Differential, and Mediation Effects

LI Dong-Ping,ZHANG Wei,LI Dan-Li,WANG Yan-Hui,ZHEN Shuang-Ju,

心理学报 , 2012,
Abstract: Youth aggression is a worldwide public health problem. Understanding the antecedents of aggression is the precursor of any successful prevention and intervention. A large body of literature shows that parenting styles and temperament are closely related to aggressive behaviors in adolescence. However, our understanding of the association among these variables is limited in several ways. First, there is a paucity of research that examines the unique effects of parenting styles and temperament on aggression. Second, work is needed that distinguishes different forms of aggression (i.e., direct vs. indirect aggression) and examines the similarity of and differences among the antecedents of these behaviors. Third, the existing research is not clear about the underlying mechanisms in the relationship between parenting styles, temperament, and aggressive behaviors. The purpose of the present study is to investigate: 1) the unique and differential associations of parenting styles and temperament with direct and indirect aggression in adolescence; 2) whether adolescents’ normative beliefs about aggression mediates the relationship between parenting styles or temperament, and direct and indirect aggression. Participants were 660 middle school students (mean age = 14.14 years, 364 females) recruited from a southern province in mainland China. In school, participants completed Parenting Styles and Dimensions Questionnaire, Early Adolescent Temperament Questionnaire (Revised Version, Short Form), and Aggressive Beliefs and Behaviors in Adolescence Scale. Multiple and multivariate regression analyses showed that (a) parenting styles (authoritative, authoritarian, and permissive) were not significantly associated with direct aggression, while temperamental characteristics (effortful control, anger/frustration, and sensation seeking) were uniquely associated with direct aggression. In contrast, parenting styles and temperament were both uniquely associated with indirect aggression. (b) Parenting styles were more strongly related to indirect aggression than to direct aggression. However, temperamental characteristics (anger/frustration and sensation seeking) were more strongly related to direct aggression than to indirect aggression. (c) Normative beliefs about direct aggression mediated the association between temperament and aggressive behaviors, while normative beliefs about indirect aggression mediated the association between parenting styles and temperament, and aggressive behaviors. In conclusion, parenting styles are to some extent specifically related to indirect aggression, whereas temperamental characteristics are specifically related to direct aggression. Normative beliefs about aggression are important mediators in the relationship between parenting styles, temperament, and aggression in adolescence.
Hostility, Physical Aggression and Trait Anger as Predictors for Suicidal Behavior in Chinese Adolescents: A School-Based Study  [PDF]
Ping Zhang, Robert E. Roberts, Zhuoya Liu, Xian Meng, Jie Tang, Lin Sun, Yizhen Yu
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0031044
Abstract: Purpose This study explored the extent to which trait aggression is associated with suicidal behavior in a nationwide school-based sample of adolescents. Methods A nationwide sample of 14,537 high school students in urban areas of China was recruited. Information concerning suicide ideation, plans, attempts, trait aggression and other risk factors was collected by a self-reported questionnaire. Multivariate regression analyses were employed to predict suicidal behavior. Results Approximately 18.5% of students reported suicide ideation, 8.7% reported suicide plans, and 4.1% reported attempts during the past one year. Hostility and trait anger had a significant positive association with suicidal ideation. Hostility and physical aggression were positively related to suicide plans. Hostility had a positive correlation with suicide attempts, while trait anger was inversely associated with suicide attempts. Conclusions This study suggests that hostility, physical aggression and trait anger may be able to be used to predict suicidal behavior among adolescents. Suicide prevention programs should target at attenuating the severity of hostility, anger and physical aggression. But teachers and parents should also give close attention to students with low trait anger.
Independence of children with Down syndrome: the experiences of families
Nunes, Michelle Darezzo Rodrigues;Dupas, Giselle;
Revista Latino-Americana de Enfermagem , 2011, DOI: 10.1590/S0104-11692011000400018
Abstract: this study develops a theoretical model concerning the experience of families of children with down syndrome in preschool and school age. the frameworks used were symbolic interactionism and grounded theory. semi-structured interviews were used as the instrument of investigation and ten families participated in the study. the theoretical model "seeking the child's independence and autonomy through constant stimulation" was identified, which shows the family's efforts to enable the child to develop the best s/he can through stimulation in order to become less dependent in the future. this model can be used to facilitate interaction with the family and can be further expanded. nurses should use spaces dedicated to care delivery to establish bonds with the family, and seek other spaces families frequent, to better meet their needs, since there are significant gaps in care and research addressing this population. instead, they should be welcomed and seen as a partner in care delivery.
A review of multivariate analyses in imaging genetics  [PDF]
Jingyu Liu,Vince D. Calhoun
Frontiers in Neuroinformatics , 2014, DOI: 10.3389/fninf.2014.00029
Abstract: Recent advances in neuroimaging technology and molecular genetics provide the unique opportunity to investigate genetic influence on the variation of brain attributes. Since the year 2000, when the initial publication on brain imaging and genetics was released, imaging genetics has been a rapidly growing research approach with increasing publications every year. Several reviews have been offered to the research community focusing on various study designs. In addition to study design, analytic tools and their proper implementation are also critical to the success of a study. In this review, we survey recent publications using data from neuroimaging and genetics, focusing on methods capturing multivariate effects accommodating the large number of variables from both imaging data and genetic data. We group the analyses of genetic or genomic data into either a priori driven or data driven approach, including gene-set enrichment analysis, multifactor dimensionality reduction, principal component analysis, independent component analysis (ICA), and clustering. For the analyses of imaging data, ICA and extensions of ICA are the most widely used multivariate methods. Given detailed reviews of multivariate analyses of imaging data available elsewhere, we provide a brief summary here that includes a recently proposed method known as independent vector analysis. Finally, we review methods focused on bridging the imaging and genetic data by establishing multivariate and multiple genotype-phenotype-associations, including sparse partial least squares, sparse canonical correlation analysis, sparse reduced rank regression and parallel ICA. These methods are designed to extract latent variables from both genetic and imaging data, which become new genotypes and phenotypes, and the links between the new genotype-phenotype pairs are maximized using different cost functions. The relationship between these methods along with their assumptions, advantages, and limitations are discussed.
Multivariate analyses of genotype x environment interaction of popcorn
Miranda, Glauco Vieira;Souza, Leandro Vagno de;Guimar?es, Lauro José Moreira;Namorato, Heraldo;Oliveira, Lucimar Rodrigues;Soares, Marcelo Oliveira;
Pesquisa Agropecuária Brasileira , 2009, DOI: 10.1590/S0100-204X2009000100007
Abstract: the objectives of this work were to evaluate the genotype x environment (gxe) interaction for popcorn and to compare two multivariate analyses methods. nine popcorn cultivars were sown on four dates one month apart during each of the agricultural years 1998/1999 and 1999/2000. the experiments were carried out using randomized block designs, with four replicates. the cv. zélia contributed the least to the gxe interaction. the cv. vi?osa performed similarly to cv. rosa-claro. optimization of gxe was obtained for cv. cms 42 for a favorable mega-environment, and for cv. cms 43 for an unfavorable environment. multivariate analysis supported the results from the method of eberhart & russell. the graphic analysis of the additive main effects and multiplicative interaction (ammi) model was simple, allowing conclusions to be made about stability, genotypic performance, genetic divergence between cultivars, and the environments that optimize cultivar performance. the graphic analysis of the genotype main effects and genotype x environment interaction (gge) method added to ammi information on environmental stratification, defining mega-environments and the cultivars that optimized performance in those mega-environments. both methods are adequate to explain the genotype x environment interactions.
On the Computation of Multivariate Scenario Sets for the Skew-t and Generalized Hyperbolic Families  [PDF]
Emanuele Giorgi,Alexander J. McNeil
Statistics , 2014,
Abstract: We examine the problem of computing multivariate scenarios sets for skewed distributions. Our interest is motivated by the potential use of such sets in the "stress testing" of insurance companies and banks whose solvency is dependent on changes in a set of financial "risk factors". We define multivariate scenario sets based on the notion of half-space depth (HD) and also introduce the notion of expectile depth (ED) where half-spaces are defined by expectiles rather than quantiles. We then use the HD and ED functions to define convex scenario sets that generalize the concepts of quantile and expectile to higher dimensions. In the case of elliptical distributions these sets coincide with the regions encompassed by the contours of the density function. In the context of multivariate skewed distributions, the equivalence of depth contours and density contours does not hold in general. We consider two parametric families that account for skewness and heavy tails: the generalized hyperbolic and the skew-t distributions. By making use of a canonical form representation, where skewness is completely absorbed by one component, we show that the HD contours of these distributions are "near-elliptical" and, in the case of the skew-Cauchy distribution, we prove that the HD contours are exactly elliptical. We propose a measure of multivariate skewness as a deviation from angular symmetry and show that it can explain the quality of the elliptical approximation for the HD contours.
Using multivariate decoding to go beyond contrastive analyses in consciousness research  [PDF]
Kristian Sandberg,Lau M. Andersen,Morten Overgaard
Frontiers in Psychology , 2014, DOI: 10.3389/fpsyg.2014.01250
Abstract: Contrasting conditions with and without awareness has been the preferred method for investigating the neural correlates of consciousness (NCC) for decades, yet recently it has been suggested that further insights can be made by moving beyond this method, specifically by meticulously controlling that potential precursors and consequences of the NCC are not mistaken for an NCC. Here, we briefly review the advantages and potential pitfalls of existing paradigms going beyond the contrastive method, and we propose multivariate decoding of neural activity patterns as a supplement to other methods. Specifically, we emphasize the ability of multivariate decoding to detect which patterns of neural activity are consistently predictive of conscious experiences at the single trial level. This is relevant as the “NCC proper” is expected to be consistently predictive whereas processes that are consequences of consciousness may not occur on every trial (making them less predictive) and prerequisites of consciousness may be present on some trials without conscious experience (making them less predictive).
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