1,721,005 research outputs found
Population size estimation via alternative parametrizations for Poisson mixture models
Full text linkWe exploit a suitable moment-based reparametrization of the Poisson mixtures distributions for developing classical and Bayesian inference for the unknown size of a finite population in the presence of count data. Here we put particular emphasis on suitable mappings between ordinary moments and recurrence coefficients that will allow us to implement standard maximization routines and MCMC routines in a more convenient parameter space. We assess the comparative performance of our approach in real data applications and in a simulation study
k-FWER control without multiplicity correction, with application to detection of genetic determinants of multiple sclerosis in Italian twins
Full text linkWe show a novel approach for k-FWER control which does not involve any correction, but only testing the hypotheses along a (possibly datadriven) order until a suitable number of p-values are found above the uncorrected α level. p-values can arise from any linear model in a parametric or non parametric setting. The approach is not only very simple and computationally light, but also the data-driven order enhances power when the sample size is small (and also when k and/or m is large). We illustrate the method on an original study about gene discovery in multiple sclerosis, in which were involved a small number of couples of twins, discordant by disease
FDR Control with Pseudo-Gatekeeping Based on a Possibly Data Driven Order of the Hypotheses
Full text linkWe propose a multiple testing procedure controlling the false discovery rate. The procedure is based on a possibly data driven ordering of the hypotheses, which are tested at the uncorrected level q until a suitable number is not rejected. When the order is data driven, larger effect sizes are considered first, therefore selecting more interesting hypotheses with larger probability. The proposed procedure is valid under independence for the test statistics. We also propose a modification which makes our procedure valid under arbitrary dependence. It is shown in simulation that we compare particularly well when the sample size is small. We conclude with an application to identification of molecular signatures of intracranial ependymoma. The methods are implemented in an R package (someMTP), freely available on CRAN. © 2013, The International Biometric Society
Error rates for multivariate outlier detection
No full textMultivariate outlier identification requires the choice of reliable cut-off points for the robust distances that measure the discrepancy from the fit provided by high-breakdown estimators of location and scatter. Multiplicity issues affect the identification of the appropriate cut-off points. It is described how a careful choice of the error rate which is controlled during the outlier detection process can yield a good compromise between high power and low swamping, when alternatives to the Family Wise Error Rate are considered. Multivariate outlier detection rules based on the False Discovery Rate and the False Discovery Exceedance criteria are proposed. The properties of these rules are evaluated through simulation. The rules are then applied to real data examples. The conclusion is that the proposed approach provides a sensible strategy in many situations of practical interest. © 2010 Elsevier B.V. All rights reserved
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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