Global ETD Search

31	The Use of Net Benefit in Modeling Non-Proportional Hazards Alharbi, Abdulwahab 12 1900 (has links) Indiana University-Purdue University Indianapolis (IUPUI) / Background: The hazard ratio (HR), representing the quantified estimate of treatment effect in survival analysis, measures the instantaneous relative difference of failure risk between two groups. The HR is typically assumed to be independent of time; however, this assumption is usually violated in practice. If the proportionality assumption holds, HR can be validly with the popular Cox proportional hazards model. When not proportional, the Wilcoxon-Gehan has been proposed to test the hypothesis of no difference. These have been recently generalized to evaluate differences in survival time for more than zero survival differences (the “net survival benefit”). Method: In this thesis, an attempt is made to illustrate the properties of generalized Wilcoxon Gehan tests as proposed by Buyse (2009). We use the concept of net survival benefit to re-analyze the trial by the Gastrointestinal Tumor Study Group (1982) by comparing chemotherapy versus combined chemotherapy and radiation in the treatment of locally unresectable gastric cancer. Survival times in days, for the 45 patients were recorded in each treatment arm. In that trial, a delayed treatment effect was observed, thus the HR is non-proportional. To provide a flexible assessment of the treatment effect, the net survival benefit was computed using datasets simulated under typical scenarios of proportional hazards, such as delayed treatment effect. Results: The generalized Wilcoxon statistic U, favored not adding radiation to chemotherapy, but only for survival up to 12 months. At Δ=0, U (0) = 491. In the simulated data sets, the confidence interval under the null hypothesis U (0) is (-152, 388). The test statistic 491 is outside this interval indicating radiation treatment might be beneficial. At U(12) = 219, it is inside the confidence interval of no treatment effect (-154,268) indicating the benefit of Chemo only is gone after 12 months. Conclusions: The net survival benefit measured via Buyse’s generalized Wilcoxon statistic is a measure of treatment effect that is meaningful whether or not hazards are proportional. The associated statistical test is more powerful than the standard log-rank test when a delayed treatment effect is anticipated. Net benefit Log-rank test Hazard Ratio Linear-rank test Randomization test Buyse's generalized Gehan test Wilcoxon test Chemotherapy plus Radiation
32	General Education Teachers Implementing Common Core with Students in Special Education: A Mixed Methods Study of Teachers' Self-Efficacy Beliefs Cash, Jon Leland 13 December 2014 (has links) This embedded mixed method study addresses the problems teachers have reported in believing themselves capable to implement the Common Core State Standards with students in special education. This study examines the effect professional development on implementing the Common Core State Standards had on the participating teachers’ self-efficacy beliefs. The participants (N=21) in this study were drawn from a 20-day professional development for teachers based on implementing the Common Core State Standards. The instrument used in the study was the Teacher Efficacy Beliefs System-Self. Data were subject to both statistical and qualitative analysis. The results of this study provide insight into the self-efficacy beliefs of the participants during and shortly after professional development about implementing the Common Core State Standards with students in special education. The Wilcoxon test of signed ranks revealed a significant increase in the TEB-S subscale areas of Accommodating Individual Differences and Managing Learning Routines, but not in Positive Classroom Climate. Qualitative analysis of data found both support for the statistical findings and also contradicted the statistical findings. Further qualitative analysis showed that practices presented in the professional development such as using the arts, formative assessment, and technology were effective in maintaining their teachers’ self-efficacy beliefs after professional development. Factors unrelated to the professional development, such as support from administrators and colleagues and poorly working technology were not supportive in carrying over the increase in teachers’ self-efficacy beliefs in implementing the Common Core State Standards with students in special education. The study is framed by Social Cognitive Theory and organized into 5 parts. Chapter I provides an overview of the study. Chapter II includes a review of literature related to teachers’ self-efficacy belief’s Common Core State Standards, and professional development. Chapter III describes the methodology of the study. Chapter IV presents the results of the analysis of data. Chapter IV reports the findings of the study and presents the conclusions of the study and ideas for future research. self-efficacy beliefs common core state standards mixed methods special education inclusion managing learning routines positive classroom climate accommodating individual differences wilcoxon test of signed ranks
33	兩母體生存函數比較之研究 / To study about the comparing two population's survival functions 傅鼎傑, Ting,Chieh Fu Unknown Date (has links) 對於生存時間的資料而言，通常我們所想要研究瞭解的是，至少存活到某特定時間點的機率，而這個機率亦即生存分析中的生存函數(survival function)。當有兩個不同的母體存在時，為了要知道這兩個母體的生存函數是否相同，在統計方法上，我們將進行一些檢定，常用的有Gehan-Wilcoxon和Cox-Mantel之兩樣本檢定，後來又有修飾型的Kolmogorov-Smirnov檢定。但是，前兩種檢定方法，只對此兩組生存函數呈現某特殊型式時，具有好的檢定力。因此，透過一些實證的研究，將上述檢定方法做有系統的整理，進而發展出一套簡單又有效率的檢定程序。再者，若檢定得此兩個母體之生存函數不相等時，如何利用Bootstrap方法，進一步對兩組生存函數之特定生存機率點或生存時間點所分別對應之生存時間或生存機率差距做推論與比較，本文將有詳細她說明；以提供研究人員更多有效的資訊，不再僅止於檢定虛無假設是否拒絕而已。最後，我們又藉由推廣上述Bootstrap方法，將其運用到檢定方法上，而另外發展出一種新的兩母體生存函數之檢定方法。 / When two different populations exist, we will take some tests by Cehan-Wilcoxon, Cox-Mantel or Modified Kolmogorov- Smirnov in satistical way. Therefore we develope a simple and efficient test process from arranging above test ways system- atically through some real study. How to use Bootstrap way to infer the difference of survival time or survival probability of specular point. We infer Bootstrap way on test work and then develope a new two populations survival function test way. 生存函數 Kaplan-Meier估計量 A<sub>n</sub>假設 Berliner-Hill估計量 Gehan-Wilcoxon檢定 Cox-Mantel檢定修飾型的Kolmogorov-Smirnov檢定 Bootstrap方法 survival function An assumption Berliner-Hill estimator Gehan-Wilcoxon test Kaplan-Meier
34	Modèle bayésien pour les prêts investisseurs Bouvrette, Mathieu January 2006 (has links) Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal. Modèle bayésien Défaut de paiement Prêts investisseurs Fonds mutuels Arbre de classification Forêt d'arbres Arbre consensus Analyse discriminante Régression logistique/probit Chaînes de Markov à sauts réversibles Test t Test de Wilcoxon d Cohen Mesures d'association
35	Multivariate non-invasive measurements of skin disorders Nyström, Josefina January 2006 (has links) <p>The present thesis proposes new methods for obtaining objective and accurate diagnoses in modern healthcare. Non-invasive techniques have been used to examine or diagnose three different medical conditions, namely neuropathy among diabetics, radiotherapy induced erythema (skin redness) among breast cancer patients and diagnoses of cutaneous malignant melanoma. The techniques used were Near-InfraRed spectroscopy (NIR), Multi Frequency Bio Impedance Analysis of whole body (MFBIA-body), Laser Doppler Imaging (LDI) and Digital Colour Photography (DCP).</p><p>The neuropathy for diabetics was studied in papers I and II. The first study was performed on diabetics and control subjects of both genders. A separation was seen between males and females and therefore the data had to be divided in order to obtain good models. NIR spectroscopy was shown to be a viable technique for measuring neuropathy once the division according to gender was made. The second study on diabetics, where MFBIA-body was added to the analysis, was performed on males exclusively. Principal component analysis showed that healthy reference subjects tend to separate from diabetics. Also, diabetics with severe neuropathy separate from persons less affected.</p><p>The preliminary study presented in paper III was performed on breast cancer patients in order to investigate if NIR, LDI and DCP were able to detect radiotherapy induced erythema. The promising results in the preliminary study motivated a new and larger study. This study, presented in papers IV and V, intended to investigate the measurement techniques further but also to examine the effect that two different skin lotions, Essex and Aloe vera have on the development of erythema. The Wilcoxon signed rank sum test showed that DCP and NIR could detect erythema, which is developed during one week of radiation treatment. LDI was able to detect erythema developed during two weeks of treatment. None of the techniques could detect any differences between the two lotions regarding the development of erythema.</p><p>The use of NIR to diagnose cutaneous malignant melanoma is presented as unpublished results in this thesis. This study gave promising but inconclusive results. NIR could be of interest for future development of instrumentation for diagnosis of skin cancer.</p> Multivariate Data Analysis Non-invasive techniques Clinical studies Principal Component Analysis Wilcoxon Signed Rank Sum Test Near-InfraRed spectroscopy Laser Doppler Imaging Digital Colour Photography Analytical chemistry Analytisk kemi
36	Aspects of analysis of small-sample right censored data using generalized Wilcoxon rank tests Öhman, Marie-Louise January 1994 (has links) The estimated bias and variance of commonly applied and jackknife variance estimators and observed significance level and power of standardised generalized Wilcoxon linear rank sum test statistics and tests, respectively, of Gehan and Prentice are compared in a Monte Carlo simulation study. The variance estimators are the permutational-, the conditional permutational- and the jackknife variance estimators of the test statistic of Gehan, and the asymptotic- and the jackknife variance estimators of the test statistic of Prentice. In unbalanced small sample size problems with right censoring, the commonly applied variance estimators for the generalized Wilcoxon rank test statistics of Gehan and Prentice may be biased. In the simulation study it appears that variance properties and observed level and power may be improved by using the jackknife variance estimator. To establish the sensitivity to gross errors and misclassifications for standardised generalized Wilcoxon linear rank sum statistics in small samples with right censoring, the sensitivity curves of Tukey are used. For a certain combined sample, which might contain gross errors, a relatively simple method is needed to establish the applicability of the inference drawn from the selected rank test. One way is to use the change of decision point, which in this thesis is defined as the smallest proportion of altered positions resulting in an opposite decision. When little is known about the shape of a distribution function, non-parametric estimates for the location parameter are found by making use of censored one-sample- and two-sample rank statistics. Methods for constructing censored small sample confidence intervals and asymptotic confidence intervals for a location parameter are also considered. Generalisations of the solutions from uncensored one-sample and two-sample rank tests are utilised. A Monte-Carlo simulation study indicates that rank estimators may have smaller absolute estimated bias and smaller estimated mean squared error than a location estimator derived from the Product-Limit estimator of the survival distribution function. The ideas described and discussed are illustrated with data from a clinical trial of Head and Neck cancer. / digitalisering@umu Variance estimation Jackknifing Influence function Gross error sensitivity Break-Down point Sensitivity curve Location parameter estimation Statistics, computer and systems science Statistik, data- och systemvetenskap
37	Modèle bayésien pour les prêts investisseurs Bouvrette, Mathieu January 2006 (has links) Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal Modèle bayésien Défaut de paiement Prêts investisseurs Fonds mutuels Arbre de classification Forêt d'arbres Arbre consensus Analyse discriminante Régression logistique/probit Chaînes de Markov à sauts réversibles Test t Test de Wilcoxon d Cohen Mesures d'association
38	Experiences of Physical Sciences teachers when introduced to an electronic expert system Mothobi, Neo Jack January 2013 (has links) This study outlines the strategies that were employed during the training of Grade 11 Physical Sciences teachers in the use and development of an Electronic Performance Support System (EPSS). The EPSS process involves extended individualised support for teachers through face-to-face training. A purposive sample was utilised and 22 Grade 11 Physical Sciences teachers participated in the study. Teachers’ skills and knowledge before and after the EPSS training process were measured on three measures of satisfaction (course material, the EPSS training process and the trainer’s competencies) and three measures regarding the EPSS (using an EPSS, creating a flowchart and designing an EPSS). A customer satisfaction index questionnaire and retrospective opinionnaire were used to collect data from the participants. Microsoft Excel was used to analyse data collected using the customer satisfaction index questionnaire. Furthermore a Statistical Package for the Social Sciences (SPSS) program was used to analyse data collected using a retrospective opinionnaire. Significant effects were found on all six measures when comparing the skills of teachers before and after attending the EPSS training programme. The results reveal that teachers who participated in the research are satisfied with the use, design and development of an EPSS in education. / Dissertation (MEd)--University of Pretoria, 2013. / gm2014 / Science, Mathematics and Technology Education / unrestricted Electronic Performance Support System Decision Support System Electronic Expert System Retrospective Opinionnaire Flowchart Algorithm Performance Matrix Wilcoxon Signed Ranked Test UCTD
39	Multivariate non-invasive measurements of skin disorders Nyström, Josefina January 2006 (has links) The present thesis proposes new methods for obtaining objective and accurate diagnoses in modern healthcare. Non-invasive techniques have been used to examine or diagnose three different medical conditions, namely neuropathy among diabetics, radiotherapy induced erythema (skin redness) among breast cancer patients and diagnoses of cutaneous malignant melanoma. The techniques used were Near-InfraRed spectroscopy (NIR), Multi Frequency Bio Impedance Analysis of whole body (MFBIA-body), Laser Doppler Imaging (LDI) and Digital Colour Photography (DCP). The neuropathy for diabetics was studied in papers I and II. The first study was performed on diabetics and control subjects of both genders. A separation was seen between males and females and therefore the data had to be divided in order to obtain good models. NIR spectroscopy was shown to be a viable technique for measuring neuropathy once the division according to gender was made. The second study on diabetics, where MFBIA-body was added to the analysis, was performed on males exclusively. Principal component analysis showed that healthy reference subjects tend to separate from diabetics. Also, diabetics with severe neuropathy separate from persons less affected. The preliminary study presented in paper III was performed on breast cancer patients in order to investigate if NIR, LDI and DCP were able to detect radiotherapy induced erythema. The promising results in the preliminary study motivated a new and larger study. This study, presented in papers IV and V, intended to investigate the measurement techniques further but also to examine the effect that two different skin lotions, Essex and Aloe vera have on the development of erythema. The Wilcoxon signed rank sum test showed that DCP and NIR could detect erythema, which is developed during one week of radiation treatment. LDI was able to detect erythema developed during two weeks of treatment. None of the techniques could detect any differences between the two lotions regarding the development of erythema. The use of NIR to diagnose cutaneous malignant melanoma is presented as unpublished results in this thesis. This study gave promising but inconclusive results. NIR could be of interest for future development of instrumentation for diagnosis of skin cancer. Multivariate Data Analysis Non-invasive techniques Clinical studies Principal Component Analysis Wilcoxon Signed Rank Sum Test Near-InfraRed spectroscopy Laser Doppler Imaging Digital Colour Photography Analytical chemistry Analytisk kemi
40	Electrostaticanalisys the Ras active site Khan, Abdul Kareem 05 March 2009 (has links) La preorganització electrostàtica del centre actiu s'ha postulat com el mecanisme genèric de l'acció dels enzims. Així, alguns residus "estratègics" es disposarien per catalitzar reaccions interaccionant en una forma més forta amb l'estat de transició, baixant d'aquesta manera el valor de l'energia dactivació g cat. S'ha proposat que aquesta preorientació electrostática s'hauria de poder mostrar analitzant l'estabilitat electrostàtica de residus individuals en el centre actiu.Ras es una proteïna essencial de senyalització i actúa com un interruptor cel.lular. Les característiques estructurals de Ras en el seu estat actiu (ON) són diferents de les que té a l'estat inactiu (OFF). En aquesta tesi es duu a terme una anàlisi exhaustiva de l'estabilitat dels residus del centre actiu deRas en l'estat actiu i inactiu. / The electrostatic preorganization of the active site has been put forward as the general framework of action of enzymes. Thus, enzymes would position "strategic" residues in such a way to be prepared to catalyze reactions byinteracting in a stronger way with the transition state, in this way decreasing the activation energy g cat for the catalytic process. It has been proposed thatsuch electrostatic preorientation should be shown by analyzing the electrostatic stability of individual residues in the active site.Ras protein is an essential signaling molecule and functions as a switch in thecell. The structural features of the Ras protein in its active state (ON state) are different than those in its inactive state (OFF state). In this thesis, an exhaustive analysis of the stability of residues in the active and inactive Ras active site is performed. dinàmica centre actiu relacions d'estructura activitat preorganització reorganització estat de transició estat actiu estabilitat electrostàtica interacción proteïna-proteïna test de ranks de Wilcoxon P-loop G1 motif HVR metastability RMSD substrate assisted catalysis sequence alignment beta sheet helix Z-test wilcoxon rank test protein-protein interactions electrostatic stability active state dynamics signal transduction electrostatic stabilization ras effectors guanine exchange factor GTPase-activating proteins quantum mechanics/molecular PDLD/S-LRA X-ray crystallography solvation energy free energy perturbation statistical analysis GTP hydrolysis guanosine diphosphate guanosine triphosphate computer simulation thermodynamics protein conformation electrostatics interruptor II interruptor I llaç P motiu G1 HVR (regions altament variables) metaestabilita RMSD catàlisi assistida pel substrat aliniament de seqüència fulla beta hèlix test Z transducció del senyal estabilització electrostàtica efectors de ras factor de bescamvi de guanina proteïnes activadores de l'activitat mecànica quàntica/mecànica PDLD/S-LRA cristalografia de raigs X energia de solvatació perturbació de l'energia lliure anàlisi estadística hidròlisi de GTP difosfat de guanosina trifosfat de guanosina simulació computacional termodinàmica conformació proteïca electrostàtica switch-I switch-II 537 576

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