1,720,956 research outputs found
Performance and robustness of single-source capture-recapture population size estimators with covariate information and potential one-inflation
No full textCapture-recapture methods for estimating the total size of elusive populations are widely-used, however, due to the choice of estimator impacting upon the results and conclusions made, the question of performance of each estimator is raised. Motivated by an application of the estimators which allow covariate information to meta-analytic data focused on the prevalence rate of completed suicide after bariatric surgery, where studies with no completed suicides did not occur, this paper explores the performance of the estimators through use of a simulation study. The simulation study addresses the performance of the Horvitz–Thompson, generalised Chao and generalised Zelterman estimators, and develops a novel, generalised, form of the modified Chao estimator to account for both covariate information and one-inflation. In addition, the performance of the analytical approach to variance computation is addressed. Given that the estimators vary in their dependence on distributional assumptions, additional simulations are utilised to address the question of the impact outliers have on performance and inference.<br/
Uni-list capture-recapture approaches, with uncertainty quantification, performance analysis and a meta-analytic application
No full textMeta-analysis is a powerful tool for evaluating numerous studies focused on the same or similar research question and integrating the results to identify a common parameter.This well-established methodology is prone to bias, so this thesis proposes the use of model-based meta-analytic and uni-list capture-recapture approaches, to compute more reliable estimates, with a focus on count data systematically missing zero counts.For the meta-analytic approach, traditional methodologies do not adequately address zero-truncated count data. This thesis develops a model-based approach with zero-truncated count models which appropriately account for the missing zeroes and an exposure variable if applicable. From these models, a maximum likelihood approach is taken with the expectation-maximisation algorithm, used to compute less biased parameter estimates. Following these approaches, both observed and unobserved heterogeneity are addressed through covariate modelling and overdispersion modelling respectively.As for the uni-list capture-recapture approach, the Horvitz-Thompson, generalised Chao’s and generalised Zelterman’s estimators are used for population size estimation, allowing for the inclusion of covariate information and an exposure variable.Also explored is the uncertainty that arises from these estimation methods, with both approximation-based variance estimation methods and the bootstrap algorithm addressed. Various approaches to the bootstrap algorithm and methods for accounting for model uncertainty are developed, in addition to alternative methods of confidence interval construction. The last focus of the thesis addresses the estimators under the presence of one-inflation, and given the poor performance of many of the existing estimators, the generalised-modified Chao’s estimator is developed to account for zero-truncation, one-inflation and covariate information.The methodologies discussed in this thesis are demonstrated through the use of real-life case study data, and assessed through a series of simulation studies
Zero-truncated modelling in a meta-analysis on suicide data after bariatric surgery
No full textMeta-analysis is a well-established method for integrating results from several independent studies to estimate a common quantity of interest. However, meta-analysis is prone to selection bias, notably when particular studies are systematically excluded. This can lead to bias in estimating the quantity of interest. Motivated by a meta-analysis to estimate the rate of completed-suicide after bariatric surgery, where studies which reported no suicides were excluded, a novel zero-truncated count modeling approach was developed. This approach addresses heterogeneity, both observed and unobserved, through covariate and overdispersion modeling, respectively. Additionally, through the Horvitz-Thompson estimator, an approach is developed to estimate the number of excluded studies, a quantity of potential interest for researchers. Uncertainty quantification for both estimation of suicide rates and number of excluded studies is achieved through a parametric bootstrapping approach
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
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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