1,720,971 research outputs found
A Quantile-based Test for Detecting Differential Expression in Microarray Data
No full textNello scorso decennio lo sviluppo di metodi statistici per l’analisi di dati di microarray è stato oggetto di crescente interesse. Un problema cruciale in questo campo è l’identificazione di geni che mostrano una differente espressione tra due o più gruppi, come ad esempio tra tessuti sani e malati. Un grande numero di strumenti statistici è stato proposto per questo compito, la maggior parte dei quali ha l’obiettivo di testare un’ipotesi di uguaglianza tra medie. Lo scopo del presente lavoro è di introdurre una statistica semplice basata sui quantili, in grado di testare differenze a diversi livelli della distribuzione, e che gode della proprieta desiderabile di invarianza rispetto a trasformazioni monotone dei dati
Modelling short-term effects of ozone on morbidity: an application to the city of Milano, Italy, 1995-2003.
No full textIn this paper, we explore a range of concerns that arise in measuring
short-term effects of ozone on health. In particular, we tackle the problem of measuring
exposure using alternative daily measures of ozone derived from hourly concentrations.
We adopt the exposure paradigm of Chiogna and Bellini (Environmetrics
13:55–69, 2002) extending it to ozone concentrations, and we compare its performances
with respect to traditional exposure measures by exploiting model selection.
To investigate the stability of model selection, we then apply the idea of bootstrapping
the modelling process
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
Jackknife empirical likelihood based confidence intervals for partial areas under ROC curves.
No full textThe partial area under the ROC curve (partial AUC) summarizes the accuracy of a diagnostic or screening
test over a relevant region of the ROC curve and represents a useful tool for the evaluation and the
comparison of tests. In this paper, we propose a jackknife empirical likelihood method for making inference
on partial AUCs. Following the idea in Jing, Yuan, and Zhou (2009), we combine the empirical
likelihood function with suitable jackknife pseudo-values obtained from a nonparametric estimator of
the normalized partial AUC. This leads to a jackknife empirical likelihood function for normalized partial
AUCs, for which a Wilks-type result is obtained. Then, such a pseudo-likelihood can be used, in a
standard way, to construct confidence intervals or perform tests of hypotheses. We also give some simulation
results that indicate that the jackknife empirical likelihood based confidence intervals compare
favorably with other alternatives in terms of coverage probability. The proposed method is extended to
inference on the difference between two partial AUCs. Finally, an application to the Wisconsin Breast
Cancer Data is 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
Graphical modelling for gene set analysis: a case-study in knockout experiments
No full textPathway signalling networks represent several tens of genes/proteins and their relations. It is expected that only small parts of these pathways will differ (will be deregulated) in different experimental conditions. Despite such expectation, till now the issue of local dereg- ulation of pathways does not seem to have been properly taken into consideration in the literature. In this paper, we aim to perform a critical appraisal of the methodology based on graphical models developed in Massa et al. (2010) that allows to decompose networks’ topologies and to monitor the dynamics of small- deregulated modules. To do this, we will use data from networks with known behaviour that offer the possibility of carrying out an realistic check of respondance of the model to changes in the experimental conditions
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
- …
