1,720,953 research outputs found
Tests for equivalence or non-inferiority of diagnostic tests
No full textΗ διάγνωση, όπως και η θεραπεία, αποτελεί κρίσιμο στοιχείο της κλινικής πρακτικής, και στατιστικές μελέτες στον χώρο της ιατρικής διεξάγονται με στόχο την ενίσχυση των διαγνωστικών μεθόδων. Διαγνωστικοί έλεγχοι (diagnostic tests) ονομάζονται
διάφοροι ιατρικοί έλεγχοι που γίνονται με σκοπό τον εντοπισμό και την πρόληψη ασθενειών. Ενδεικτικά παραδείγματα διαγνωστικών ελέγχων είναι οι αιματολογικές εξετάσεις, το τεστ Παπανικολάου, η μαστογραφία, ο υπέρηχος άνω και κάτω κοιλίας κ.ά. Σκοπός της διενέργειας των διαγνωστικών ελέγχων είναι ο εντοπισμός
ασθενειών που δεν μπορούν να φανούν με άλλον τρόπο ή ο
εντοπισμός της νόσου σε πρώιμο στάδιο, δηλαδή πριν την εμφάνιση
συμπτωμάτων, ώστε να αντιμετωπιστεί εγκαίρως και
αποτελεσματικά. Κοινό χαρακτηριστικό των διαγνωστικών ελέγχων είναι ότι η εμφάνιση θετικού αποτελέσματος σημαίνει ότι είναι πιθανό το άτομο που υποβλήθηκε στον έλεγχο να έχει την υπό εξέταση νόσο και αυτό σημαίνει ότι θα πρέπει να υποβληθεί σε εξετάσεις μεγαλύτερης ακρίβειας ή ακόμη και κατευθείαν σε θεραπεία. Από τα παραπάνω συμπεραίνουμε ότι η χρησιμότητα ενός διαγνωστικού ελέγχου προσδιορίζεται μεταξύ άλλων από την ακρίβεια με την οποία διακρίνει τα άτομα σε αυτά με ή χωρίς το υπό διερεύνηση νόσημα. Είναι φανερό ότι προϋπόθεση για την αξιολόγηση της διακριτικής ικανότητας ενός ελέγχου είναι η σίγουρη γνώση της ομάδας ασθενών, η οποία γνώση εξασφαλίζεται μέσω των αποτελεσμάτων σε μία διαγνωστική μέθοδο που θεωρείται σημείο αναφοράς (gold standard) και η οποία αποκαλύπτει την πραγματική κλινική κατάσταση του ασθενή. Χαρακτηριστικό παράδειγμα μεθόδου αναφοράς είναι η βιοψία. Στη σημερινή εποχή είναι όλο και πιο δύσκολο να αναπτυχθούν νέοι διαγνωστικοί έλεγχοι με μεγαλύτερη διακριτική ικανότητα από τη μέθοδο αναφοράς. Επιπρόσθετα, οι μέθοδοι αναφοράς τις περισσότερες φορές είτε έχουν υψηλό κόστος ή είναι χρονοβόρες και δεν είναι εύκολες στην εφαρμογή τους. Αυτό έχει οδηγήσει να εισαχθούν στη βιβλιογραφία στατιστικοί τρόποι ελέγχου ότι μία διαγνωστική μέθοδος έχει ισοδύναμη ή μη κατώτερη αποτελεσματικότητα σε σχέση με μία υπάρχουσα καθιερωμένη.Η παρουσίαση των παραπάνω στατιστικών ελέγχων όταν τα διαθέσιμα δεδομένα είναι εξαρτημένα δίτιμα (ασθενής-όχι ασθενής) αποτελεί το βασικό αντικείμενο μελέτης αυτής της μεταπτυχιακής διατριβής. Στο παραπάνω πλαίσιο, η διάρθρωση του υπολοίπου της διατριβής έχει ως εξής. Στο Κεφάλαιο 1 (Εισαγωγή) παρουσιάζονται οι έννοιες της ισοδυναμίας και της μη κατωτερότητας μεταξύ δύο διαγνωστικών ελέγχων, καθώς και η πρακτική αξία τους στους διάφορους κλάδους της ιατρικής. Τα Κεφάλαια 2 έως 4 περιλαμβάνουν μια ανασκόπηση των βασικών μεθόδων που προτάθηκαν στη βιβλιογραφία για την αξιολόγηση της ισοδυναμίας ή της μη κατωτερότητας μιας νέας διαγνωστικής μεθόδου, σε σύγκριση με μια αποδεδειγμένα αποτελεσματική και ευρέως χρησιμοποιούμενη μέθοδο. Ειδικότερα, οι μέθοδοι ταξινομούνται στα τρία αυτά κεφάλαια ως προς την παράμετρο που χρησιμοποιείται για τη σύγκριση της απόδοσης των διαγνωστικών ελέγχων (διαφορά πιθανοτήτων, λόγος πιθανοτήτων κ.ο.κ.). Στο Κεφάλαιο 5 (Συγκριτικές μελέτες) παρατίθενται και αναλύονται τα αποτελέσματα των συγκριτικών μελετών, που έχουν εμφανιστεί στη βιβλιογραφία με σκοπό την αξιολόγηση και τη σύγκριση της επίδοσης των υπό εξέταση μεθόδων. Στο Κεφάλαιο 6 (Επίλογος) συνοψίζονται τα συμπεράσματα αυτής της μεταπτυχιακής διατριβής και δίνονται προτάσεις για περαιτέρω έρευνα. Τέλος, η μεταπτυχιακή διατριβή ολοκληρώνεται με τη Βιβλιογραφία.Diagnosis of a disease is a critical element of clinical practice, and medical statistical studies are conducted to enhance diagnostic methods. Various medical tests performed for the purpose of disease detection and prevention are called diagnostic tests. Examples of diagnostic tests include blood tests, the Pap test, mammography, upper and lower abdominal ultrasound, etc. The purpose of carrying out diagnostic tests is either the identification of a disease that cannot be detected in any other way or the detection of a disease at an early stage. A positive result in a diagnostic test typically indicates a possible presence of the disease, suggesting the need for further testing or the initiation of treatment. he usefulness of a diagnostic test is determined, among other factors, by its accuracy in distinguishing between individuals with and without the disease. It is clear that evaluating the discriminative power of a test requires reliable knowledge of the patient’s disease status, which is typically established using a reference (gold standard) diagnostic method, such as a biopsy. Today, it is increasingly difficult to develop new diagnostic tests with a higher discriminative power than the reference method. In addition, reference methods are most often either expensive or time-consuming and not easy to implement. This prompted the introduction of statistical techniques of examining whether a diagnostic method has equivalent or non-inferior efficacy to an existing established method. The presentation of the available statistical methodology when the available data are paired binary (patient- non patient) is the main objective of the study in this master's thesis. In the above context, the structure of the remainder of the thesis is as follows. Chapter 1 (Introduction) gives an initial idea of the concepts of equivalence and non-inferiority between two diagnostic tests, and their practical value in different branches of medicine. Chapters 2-4 include a review of the main methods proposed in the literature for assessing the equivalence or non-inferiority of a new diagnostic method, compared with a proven and widely used method, classified according to the parameter of evaluation used. Chapter 5 analyses the results of the comparative studies to evaluate the performance of the methods presented in the previous chapters. Chapter 6 summarizes the conclusions of this thesis and provides suggestions for further research. Finally, the thesis concludes with the Bibliography.97 σ
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
Author Under Sail The Imagination of Jack London, 1893-1902
No full textIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Intro -- Title Page -- Copyright Page -- Dedication -- Contents -- Acknowledgments -- Introduction -- 1. Spirit Truth -- 2. From Absorption to Theatricality and Back Again -- 3. "I Will Build a New Present" -- 4. Sons as Authors -- 5. Fathers as Publishers -- 6. The Daughter as Author -- 7. Lovers as Authors -- 8. At Sea with the Family -- 9. Yellow News, Yellow Stories -- 10. The Return Home -- Notes -- Bibliography -- Index -- About Jay WilliamsIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Description based on publisher supplied metadata and other sources.Electronic reproduction. Ann Arbor, Michigan : ProQuest Ebook Central, YYYY. Available via World Wide Web. Access may be limited to ProQuest Ebook Central affiliated libraries
- …
