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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
111

Stress Testing the Italian Banking System during the Global Financial Crisis

Messina, Jacopo January 2011 (has links)
This study performs a stress testing exercise on the Italian banking system in view of the 2007 financial crisis which was triggered by the crash of subprime mortgages. At the base of the global financial crisis was a failure of finan- cial regulators to quantify the accumulation of endogenous risks. Following the crisis, stress testing has acquired particular emphasis in the field of risk measurement under the Basel II supervisory framework. An econometric rela- tionship between the probability of default and the macroeconomic indicators is modeled according to the Merton approach for structural analysis using data on the Italian banking system. A latent factor model is employed to under- stand the dependence of the credit risk on the changes in the macroeconomic environment. The resulting relationship is exploited to compute the capital requirement under stressed conditions in order to draw inference about the resilience of the Italian banking system. JEL Classification G0, G01, G17, G10, C50, C22 Keywords Financial crisis, macroeconomic stress testing, credit risk, latent-factor model Author's e-mail jacomessi@yahoo.it Supervisor's e-mail petr.gapko@seznam.cz Abstrakt Klasifikace JEL G0, G01, G17, G10, C50, C22 Klíčová slova Financial crisis, macroeconomic stress test- ing, credit risk,...
112

A numerical case study on the sensitivity of latent heat-flux and cloudiness to the distribution of land-use

Friedrich, Katja, Mölders, Nicole 18 November 2016 (has links) (PDF)
The accomplished case studies focus on the influence of land-use on the distributions of latent heat-fluxes and cloud-water. The numerical case studies were performed with the threedimensional non-hydrostatic Mesoscale-Model GESIMA for different land-use distributions applying always the same initial conditions of a cloudy day in spring with a geostrophic wind of 8 m/s from the west. The cloud-water distributions at different times and at different levels, their temporal development, the daily sums of the domain-averaged latent heat-fluxes and cloud-water mixing ratios were investigated. Even simple initial conditions (no orography, stable atmosphere) and simple pattern in the land-use distributions emphasize that the influence of surface heterogeneity on meteorological processes cannot be neglected. As shown in this case study, land-use distribution influences the distribution and the amount of cloud-water as weil as the latent heat-flux. On the whole, all these processes are very complex and non-linear. / Die durchgeführten Sensitivitätsstudien konzentrieren sich auf den Einfluß der Landnutzungsverteilung auf die Flüsse latenter Wärme und das Wolkenwasser. Die numerischen Untersuchungen wurden mit dem dreidimensionalen nicht-hydrostatischen Mesoskalen-Modell GESIMA für verschiedene Landnutzungsmuster unter immer den gleichen meteorologischen Anfangsbedingungen für einen bewölkten Frühlingstag mit einem geostrophischen Wind von 8 m/s durchgeführt. Die Wolkenwasserverteilung zu bestimmten Zeiten und in bestimmten Niveaus, die zeitliche Entwicklung der Wolkenwasserverteilung, die Tagessummen der Gebietsmittelwerte der Flüsse latenter Wärme und des Wolkenwassers werden untersucht. Auch einfache Randbedingungen (keine Orographie, stabile, atmosphärische Bedingungen) und einfache Landnutzungsverteilungsmuster machen deutlich, daß der Einfluß der Heterogenität der Unterlage auf meteorologische Prozesse nicht zu vernachlässigen ist. Sie kann entscheidend die Verteilungen der Flüsse latenter Wärme und des Wolkenwassers beeinflussen. Die damit verbundenen Prozesse sind äußerst komplex und nicht linear.
113

Who is Going to Win the EURO 2008? A Statistical Investigation of Bookmakers Odds.

Leitner, Christoph, Zeileis, Achim, Hornik, Kurt January 2008 (has links) (PDF)
This June one of the biggest and most popular sports tournaments will take place in Austria and Switzerland, the European soccer championship 2008 (UEFA EURO 2008). Therefore millions of soccer fans in Europe and throughout the world are asking themselves: "Who is going to win the EURO 2008?" Many people, including sports experts and former players, give their guesses and expectations in the media, but there is also a group with financial incentives, like some economists who expect economical increases for the country of the winning team and bookmakers and their customers who directly make money with their beliefs. Some predictions are only guesses, but other predictions are based on quantitative methods, such as the studies of UBS Wealth Management Research Switzerland and the Raiffeisen Zentralbank. In this report we will introduce a new method for predicting the winner. Whereas other prediction methods are based on historical data, e.g., the Elo rating, or the FIFA/Coca Cola World rating, our method is based on current expectations, the bookmakers odds for winning the championship. In particular we use the odds for winning the championship for each of the 16 teams of 45 international bookmakers. By interpreting these odds as rating of the expected strength of the teams by the bookmakers, we derive a consensus rating by modelling the log-odds using a random-effects model with a team-specific random effect and a bookmaker-specific fixed effect. The consensus rating of a team can be used as an estimator for the unknown "true" strength of a team. Our method predicts team Germany with a probability of about 18.7% as the EURO 2008 winner. We predict also that the teams playing the final will be Germany and Spain with a probability of 13.9%, where Germany will win with a probability of 55%. In our study, Italy, the favorite according to the current FIFA/Coca Cola World ranking and Elo ranking, has a much lower probability than these teams to win the tournament: only 10.6%. The defending champion Greece has low chances to win the title again: about 3.4%. Furthermore, the expected performance of the host countries, Austria and Switzerland, is much better in the bookmakers consensus than in the retrospective Elo and FIFA/Coca Cola World ratings, i.e., indicating an (expected) home court advantage. Despite the associated increase in the winning probabilities, both teams have rather poor chances to win the tournament with probabilities of 1.3% and 4.0%, respectively. In a group effect study we investigate how much the classification into the four groups (A-D) affects the chance for a team to win the championship. / Series: Research Report Series / Department of Statistics and Mathematics
114

The comparison of treatments with ordinal responses. / CUHK electronic theses & dissertations collection

January 2011 (has links)
In this thesis, we focus on the the comparison of treatments with ordered categorical responses. The three cases of treatment comparisons will all be studied. The main objective of this thesis is to develop more effective comparison methods for treatments with ordinal responses and to address some important issues involved in different comparison problems. Our major statistical approach is to consider ordinal responses as manifestations of some underlying continuous random variables. / The comparison of treatments to detect possible treatment effects is a very important topic in statistical research. It has been drawing significant interests from both academicians and practitioners. Important research work on treatment comparisons dates back several decades. For treatment comparisons, the following three cases are very common: the comparison of two independent treatments; the comparison of treatments with repeated measurements; and the multiple comparison of several treatments. For different cases, the involved research issues are usually different. In many fields of study, the level of measurement for responses of the treatments is ordinal. Many examples can be found in areas such as biostatistics, psychology, sociology, and market research, where the ordered categorical variables play an important role. / This thesis consists of three main parts. In the first part, we consider the modeling of treatments with longitudinal ordinal responses by a latent growth curve. On the basis of such a latent growth curve, we achieve a comprehensive flexible model with straightforward interpretations and a variety of applications including treatment comparison, the analysis of covariates, and equivalence test of treatments. In the second part, we consider the comparison of several treatments with a control for ordinal responses. By considering the ordinal responses as manifestations of some underlying normal random variables, a latent normal distribution model is utilized and the corresponding parameter estimation method is proposed. Further, we also derive testing procedures that compare several treatments with a control under an analytical framework. Both single-step and stepwise procedures are introduced, and these procedures are compared in terms of average power based on a simulation study. In the last part of this thesis, we establish a unified framework for treatment comparisons with ordinal responses, which allows various treatment comparison methods be comprehended using a unified perspective. The latent variable model is also utilized, but the underlying random variables are allowed to have any member of the location-scale distribution family. This latent variable model under such a specification of underlying distributions subsumes many existing models in the literature. A two-step procedure to identify the model and produce the parameter estimates is proposed. Based on this procedure, many important statistical inferences can be conveniently conducted. Furthermore, the sample size determination method based on the latent variable method is also proposed. The proposed latent variable method is compared with the existing methods in terms of power and sample size. / Lu, Tongyu. / Adviser: Wai-Yin Poon. / Source: Dissertation Abstracts International, Volume: 73-06, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references (leaves 94-101). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [201-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.
115

Learning non-Gaussian factor analysis with different structures: comparative investigations on model selection and applications. / 基於多種結構的非高斯因數分析的模型選擇學習演算法比較研究及其應用 / CUHK electronic theses & dissertations collection / Ji yu duo zhong jie gou de fei Gaosi yin shu fen xi de mo xing xuan ze xue xi yan suan fa bi jiao yan jiu ji qi ying yong

January 2012 (has links)
高維資料的隱含結構挖掘是機器學習、模式識別和生物資訊學等領域中的重要問題。本論文從實踐和理論上研究了具有不同隱含結構模式的非高斯因數分析(Non-Gaussian Factor Analysis)模型。本文既從兩步法又從自動法的角度重點研究確定隱因數個數的模型選擇問題,及其在模式識別和生物資訊學上的實際應用。 / 非高斯因數分析在單高斯因數的情況下退化為傳統的因數分析(Factor Analysis)模型。我們發展了一套系統地比較模型選擇方法性能的工具,比較研究了經典的模型選擇準則(比如AIC 等),及近年來基於隨機矩陣理論的統計檢驗方法,還有貝葉斯陰陽(Bayesian Ying-Yang)和諧學習理論。同時,我們也對四個經典準則提供了一個適用於小樣本的低估因數數目傾向的相對排序的理論結果。 / 基於傳統的因數分析模型,我們還研究了參數化形式對模型選擇方法的性能的影響,一個重要的但被忽略或很少研究的問題,因為似然函數等價的參數化形式在傳統的模型選擇準則像AIC 下不會有性能差異。但是,我們通過大量的模擬資料和實際資料上的結果發現,在兩個常用的似然函數等價的因數分析參數化形式中,其中一個更加有利於在變分貝葉斯(Variational Bayes)和貝葉斯陰陽理論框架下做模型選擇。 進一步地,該兩個參數化形式被作為兩端拓展成一系列具有等價似然函數的參數化形式。實驗結果更加可靠地揭示了參數化形式的逐漸變化對模型選擇的影響。同時,實驗結果也顯示參數先驗分佈的引入可以提高模型選擇的準確度,並給出了相應的新的學習演算法。系統比較表明,不僅是兩步法還是自動法,貝葉斯陰陽學習理論都比變分貝葉斯的模型選擇的性能更佳,並且能在有利的參數化形式中獲得更大的提高。 / 二元因數分析(Binary FA)也是一種非高斯因數分析模型,它用伯努利因數去解釋隱含結構。首先,我們引入一種叫做正則對偶(canonical dual)的方法去解決在二元因數分析學習演算法中遇到的一個計算複雜度很大的二值二次規劃(Binary Quadratic Programming)問題。雖然它不能準確找到二值二次規劃的全域最優,它卻提高了整個學習演算法的計算速度和自動模型選擇的準確性。由此表明,局部嵌套的子優化問題的解不需要太精確反而能對整個學習演算法的性能更有利。然後,先驗分佈的引入進一步提高了模型選擇的性能,並且貝葉斯陰陽學習理論被系統的實驗結果證實要優於變分貝葉斯。接著,我們進一步發展了一個適用於二值資料的二元矩陣分解演算法。該演算法有理論的結果保證它的性能,並且在實際應用中,能以比其他相關演算法更優的性能從大規模的蛋白相互作用網路中檢測出蛋白功能複合物。 / 進一步,我們在一個半盲(semi-blind)的框架下研究了非高斯因數分析的演算法及其在系統生物學中的應用。非高斯因數分析模型被用於基因轉錄調控建模,並引入稀疏約束到連接矩陣,從而提出一個能有效估計轉錄因數調控信號的方法,而不需要像網路分量分析(Network Component Analysis)方法那樣預先給定轉錄因數調控基因的拓撲網路結構。特別地,借助二元因數分析,調控信號中的二元特徵能被直接捕捉。這種似開關的模式在很多生物過程的調控機制裡面起著重要作用。 / 最後,基於半盲非高斯因數分析學習演算法,我們提出了一套分析外顯子測序數據的方法,能有效地找出與疾病關聯的易感基因,提供了一個可能的方向去解決傳統的全基因組關聯分析(GWAS)方法在低頻高雜訊的外顯子測序數據上失效的問題。在一個1457 個樣本的大規模外顯子測序數據的初步結果顯示,我們的方法既能確認很多已經被認為是與疾病相關的基因,又能找到新的被重複驗證有顯著性的易感基因。相關的表達譜資料進一步顯示所找到的新基因在疾病和對照上有顯著的上下調的表達差異。 / Mining the underlying structure from high dimensional observations is of critical importance in machine learning, pattern recognition and bioinformatics. In this thesis, we, empirically or theoretically, investigate non-Gaussian Factor Analysis (NFA) models with different underlying structures. We focus on the problem of determining the number of latent factors of NFA, from two-stage approach model selection to automatic model selection, with real applications in pattern recognition and bioinformatics. / We start by a degenerate case of NFA, the conventional Factor Analysis (FA) with latent Gaussian factors. Many model selection methods have been proposed and used for FA, and it is important to examine their relative strengths and weaknesses. We develop an empirical analysis tool, to facilitate a systematic comparison on model selection performances of not only classical criteria (e.g., Akaike’s information criterion or shortly AIC) but also recently developed methods (e.g., Kritchman & Nadler’s hypothesis tests), as well as the Bayesian Ying-Yang (BYY) harmony learning. Also, we prove a theoretical relative order of underestimation tendency of four classical criteria. / Then, we investigate how parameterizations affect model selection performance, an issue that has been ignored or seldom studied since traditional model selection criteria, like AIC, perform equivalently on different parameterizations that have equivalent likelihood functions. Focusing on two typical parameterizations of FA, one of which is found to be better than the other under both Variational Bayes (VB) and BYY via extensive experiments on synthetic and real data. Moreover, a family of FA parameterizations that have equivalent likelihood functions are presented, where each one is featured by an integer r, with the two known parameterizations being both ends as r varies from zero to its upper bound. Investigations on this FA family not only confirm the significant difference between the two parameterizations in terms of model selection performance, but also provide insights into what makes a better parameterization. With a Bayesian treatment to the new FA family, alternative VB algorithms on FA are derived, and also BYY algorithms on FA are extended to be equipped with prior distributions on the parameters. A systematic comparison shows that BYY generally outperforms VB under various scenarios including varying simulation configurations and incrementally adding priors to parameters, as well as automatic model selection. / To describe binary latent features, we proceed to binary factor analysis (BFA), which considers Bernoulli factors. First, we introduce a canonical dual approach to tackling a difficult Binary Quadratic Programming (BQP) problem encountered as a computational bottleneck in BFA learning. Although it is not an exact BQP solver, it improves the learning speed and model selection accuracy, which indicates that some amount of error in solving the BQP, a problem nested in the hierarchy of the whole learning process, brings gain on both computational efficiency and model selection performance. The results also imply that optimization is important in learning, but learning is not just a simple optimization. Second, we develop BFA algorithms under VB and BYY to incorporate Bayesian priors on the parameters to improve the automatic model selection performance, and also show that BYY is superior to VB under a systematic comparison. Third, for binary observations, we propose a Bayesian Binary Matrix Factorization (BMF) algorithm under the BYY framework. The performance of the BMF algorithm is guaranteed with theoretical proofs and verified by experiments. We apply it to discovering protein complexes from protein-protein interaction (PPI) networks, an important problem in bioinformatics, with outperformance comparing to other related methods. / Furthermore, we investigate NFA under a semi-blind learning framework. In practice, there exist many scenarios of knowing partially either or both of the system and the input. Here, we modify Network Component Analysis (NCA) to model gene transcriptional regulation in system biology by NFA. The previous hardcut NFA algorithm is extended here as sparse BYY-NFA by considering either or both of a priori connectivity and a priori sparse constraint. Therefore, the a priori knowledge about the connection topology of the TF-gene regulatory network required by NCA is not necessary for our NFA algorithm. The sparse BYY-NFA can be further modified to get a sparse BYY-BFA algorithm, which directly models the switching patterns of latent transcription factor (TF) activities in gene regulation, e.g., whether or not a TF is activated. Mining switching patterns provides insights into exploring regulation mechanism of many biological processes. / Finally, the semi-blind NFA learning is applied to identify those single nucleotide polymorphisms (SNPs) that are significantly associated with a disease or a complex trait from exome sequencing data. By encoding each exon/gene (which may contain multiple SNPs) as a vector, an NFA classifier, obtained in a supervised way on a training set, is used for prediction on a testing set. The genes are selected according to the p-values of Fisher’s exact test on the confusion tables collected from prediction results. The selected genes on a real dataset from an exome sequencing project on psoriasis are consistent in part with published results, and some of them are probably novel susceptible genes of the disease according to the validation results. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Tu, Shikui. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references (leaves 196-212). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese. / Abstract --- p.i / Acknowledgement --- p.iv / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Background --- p.1 / Chapter 1.1.1 --- Motivations --- p.1 / Chapter 1.1.2 --- Independent Factor Analysis (IFA) --- p.2 / Chapter 1.1.3 --- Learning Methods --- p.6 / Chapter 1.2 --- Related Work --- p.14 / Chapter 1.2.1 --- Learning Gaussian FA --- p.14 / Chapter 1.2.2 --- Learning NFA --- p.16 / Chapter 1.2.3 --- Learning Semi-blind NFA --- p.18 / Chapter 1.3 --- Main Contribution of the Thesis --- p.18 / Chapter 1.4 --- Thesis Organization --- p.25 / Chapter 1.5 --- Publication List --- p.27 / Chapter 2 --- FA comparative analysis --- p.31 / Chapter 2.1 --- Determining the factor number --- p.32 / Chapter 2.2 --- Model Selection Methods --- p.34 / Chapter 2.2.1 --- Two-Stage Procedure and Classical Model Selection Criteria --- p.34 / Chapter 2.2.2 --- Kritchman&Nadler's Hypothesis Test (KN) --- p.35 / Chapter 2.2.3 --- Minimax Rank Estimation (MM) --- p.37 / Chapter 2.2.4 --- Minka's Criterion (MK) for PCA --- p.38 / Chapter 2.2.5 --- Bayesian Ying-Yang (BYY) Harmony Learning --- p.39 / Chapter 2.3 --- Empirical Analysis --- p.42 / Chapter 2.3.1 --- A New Tool for Empirical Comparison --- p.42 / Chapter 2.3.2 --- Investigation On Model Selection Performance --- p.44 / Chapter 2.4 --- A Theoretic Underestimation Partial Order --- p.49 / Chapter 2.4.1 --- Events of Estimating the Hidden Dimensionality --- p.49 / Chapter 2.4.2 --- The Structural Property of the Criterion Function --- p.49 / Chapter 2.4.3 --- Experimental Justification --- p.54 / Chapter 2.5 --- Concluding Remarks --- p.58 / Chapter 3 --- FA parameterizations affect model selection --- p.70 / Chapter 3.1 --- Parameterization Issue in Model Selection --- p.71 / Chapter 3.2 --- FAr: ML-equivalent Parameterizations of FA --- p.72 / Chapter 3.3 --- Variational Bayes on FAr --- p.74 / Chapter 3.4 --- Bayesian Ying-Yang Harmony Learning on FAr --- p.77 / Chapter 3.5 --- Empirical Analysis --- p.82 / Chapter 3.5.1 --- Three levels of investigations --- p.82 / Chapter 3.5.2 --- FA-a vs FA-b: performances of BYY, VB, AIC, BIC, and DNLL --- p.84 / Chapter 3.5.3 --- FA-r: performances of VB versus BYY --- p.87 / Chapter 3.5.4 --- FA-a vs FA-b: automatic model selection performance of BYYandVB --- p.90 / Chapter 3.5.5 --- Classification Performance on Real World Data Sets --- p.92 / Chapter 3.6 --- Concluding remarks --- p.93 / Chapter 4 --- BFA learning versus optimization --- p.104 / Chapter 4.1 --- Binary Factor Analysis --- p.105 / Chapter 4.2 --- BYY Harmony Learning on BFA --- p.107 / Chapter 4.3 --- Empirical Analysis --- p.108 / Chapter 4.3.1 --- BIC and Variational Bayes (VB) on BFA --- p.108 / Chapter 4.3.2 --- Error in solving BQP affects model selection --- p.110 / Chapter 4.3.3 --- Priors over parameters affect model selection --- p.114 / Chapter 4.3.4 --- Comparisons among BYY, VB, and BIC --- p.115 / Chapter 4.3.5 --- Applications in recovering binary images --- p.116 / Chapter 4.4 --- Concluding Remarks --- p.117 / Chapter 5 --- BMF for PPI network analysis --- p.124 / Chapter 5.1 --- The problem of protein complex prediction --- p.125 / Chapter 5.2 --- A novel binary matrix factorization (BMF) algorithm --- p.126 / Chapter 5.3 --- Experimental Results --- p.130 / Chapter 5.3.1 --- Other methods in comparison --- p.130 / Chapter 5.3.2 --- Data sets --- p.131 / Chapter 5.3.3 --- Evaluation criteria --- p.131 / Chapter 5.3.4 --- On altered graphs by randomly adding and deleting edges --- p.132 / Chapter 5.3.5 --- On real PPI data sets --- p.137 / Chapter 5.3.6 --- On gene expression data for biclustering --- p.137 / Chapter 5.4 --- A Theoretical Analysis on BYY-BMF --- p.138 / Chapter 5.4.1 --- Main results --- p.138 / Chapter 5.4.2 --- Experimental justification --- p.140 / Chapter 5.4.3 --- Proofs --- p.143 / Chapter 5.5 --- Concluding Remarks --- p.147 / Chapter 6 --- Semi-blind NFA: algorithms and applications --- p.148 / Chapter 6.1 --- Determining transcription factor activity --- p.148 / Chapter 6.1.1 --- A brief review on NCA --- p.149 / Chapter 6.1.2 --- Sparse NFA --- p.150 / Chapter 6.1.3 --- Sparse BFA --- p.156 / Chapter 6.1.4 --- On Yeast cell-cycle data --- p.160 / Chapter 6.1.5 --- On E. coli carbon source transition data --- p.166 / Chapter 6.2 --- Concluding Remarks --- p.170 / Chapter 7 --- Applications on Exome Sequencing Data Analysis --- p.172 / Chapter 7.1 --- From GWAS to Exome Sequencing --- p.172 / Chapter 7.2 --- Encoding An Exon/Gene --- p.173 / Chapter 7.3 --- An NFA Classifier --- p.175 / Chapter 7.4 --- Results --- p.176 / Chapter 7.4.1 --- Simulation --- p.176 / Chapter 7.4.2 --- On a real exome sequencing data set: AHMUe --- p.177 / Chapter 7.5 --- Concluding Remarks --- p.186 / Chapter 8 --- Conclusion and FutureWork --- p.187 / Chapter A --- Derivations of the learning algorithms on FA-r --- p.190 / Chapter A.1 --- The VB learning algorithm on FA-r --- p.190 / Chapter A.2 --- The BYY learning algorithm on FA-r --- p.193 / Bibliography --- p.195
116

The central role of stress relief in video gaming motivations and preferences

Schallock, Jessica Marie January 2019 (has links)
Video games are played by more than 1.8 billion people and are a pervasive force in society, but despite decades of research there has been little consensus on their effects. Before we are able to model complex outcomes such as excessive engagement, we must first understand how and why people play video games. This dissertation integrates latent factor models with techniques from machine learning and network analysis to develop a holistic picture of gaming style, motivations, and individual differences. It employs diverse sources of data across several studies and a total of 2,143 participants, combining online questionnaires with qualitative analysis of participant responses and objective information about gaming behaviour from the API of the popular gaming network "Steam", and finds that stress relief is a primary motivation for engaging in the immersive worlds of video games. Previous research has indicated three underlying factors of Immersion, Achievement and Socialising which replicated across three comprehensive studies of 480 adults, 106 adults and children with an Autism Spectrum Condition, and 961 adults and adolescents. Gamers experiencing more stress in their daily lives were more likely to have Immersion rather than Social or Achievement play styles. Achievement-oriented gamers tended to be lower in stress, higher in conscientiousness and emotional stability, and played more than Immersion-focused gamers. A qualitative analysis of 54 gamers' descriptions of why they recently chose to play a game was used to develop the "Reasons for Playing Video Games" items (RPVG), which were administered to independent samples of 243, 299 and 961 gamers. The qgraph R package was used to perform network analyses of the RPVG items and gameplay style factors, employing the machine learning-based adaptive LASSO technique to estimate a partial correlation matrix from a set of variables as a Pairwise Markov Random Field. Gamers higher in Immersion tended to play for escapism, distraction, and fantasy, while social gamers played for excitement, energy, and self-expression. Network analysis and graph theory illustrate the central role of stress relief in the network of Reasons for Playing Video Games and shows that playing when feeling stressed is strongly linked with Immersion.
117

Statistical Methods for Integrated Cancer Genomic Data Using a Joint Latent Variable Model

Drill, Esther January 2018 (has links)
Inspired by the TCGA (The Cancer Genome Atlas), we explore multimodal genomic datasets with integrative methods using a joint latent variable approach. We use iCluster+, an existing clustering method for integrative data, to identify potential subtypes within TCGA sarcoma and mesothelioma tumors, and across a large cohort of 33 dierent TCGA cancer datasets. For classication, motivated to improve the prediction of platinum resistance in high grade serous ovarian cancer (HGSOC) treatment, we propose novel integrative methods, iClassify to perform classication using a joint latent variable model. iClassify provides eective data integration and classication while handling heterogeneous data types, while providing a natural framework to incorporate covariate risk factors and examine genomic driver by covariate risk factor interaction. Feature selection is performed through a thresholding parameter that combines both latent variable and feature coecients. We demonstrate increased accuracy in classication over methods that assume homogeneous data type, such as linear discriminant analysis and penalized logistic regression, and improved feature selection. We apply iClassify to a TCGA cohort of HGSOC patients with three types of genomic data and platinum response data. This methodology has broad applications beyond predicting treatment outcomes and disease progression in cancer, including predicting prognosis and diagnosis in other diseases with major public health implications.
118

Adolescent Self-Regulation and the Influence of Peer Victimization: Examining Dynamic Interactions

Knoble, Naomi 18 August 2015 (has links)
Self-regulation is essential for successful social functioning, yet more remains to be understood about the influence of peers on this important developmental skill. This study examined the influence of verbal peer victimization on the growth of self-regulation across four years of early adolescence using parallel process growth modeling. For all adolescents, higher levels of self-regulation buffered early adolescents from the effects of negative peer interactions. In addition, early adolescents with initially low levels of self-regulation also had higher levels of depression and experienced higher levels of peer victimization than their better regulated peers. Importantly the Family Check-Up, a brief preventative intervention, resulted in improvements in self-regulation that was sustained over time. The relationship between peer victimization and self-regulation was not predictive; however, a significant persisting association was observed suggesting that improvements in adolescent self-regulation abilities help buffer youth from the impact of negative peer interactions. This research highlights the importance of the social context on the development of self-regulation during adolescence and contributes novel findings of the effect of contextual variables on self-regulation development. These findings support an ecological prevention approach, including family-centered intervention and social-emotional curricula, to promote increased self-regulation and reduce peer victimization among adolescents.
119

Social and emotional adjustment across aggressor/victim subgroups: Do aggressive-victims possess unique risk?

OConnor, Kelly E 01 January 2018 (has links)
Both theory and empirical evidence support the existence of “aggressive-victims,” a subgroup of youth who have been found to experience the negative outcomes associated with being an aggressor and being a victim. It remains unclear, however, if aggressive-victims possess risk factors that are unique from youth who are either aggressive or victimized. The present study sought to: (a) identify subgroups of seventh grade adolescents who differ in their patterns of aggression and victimization, (b) determine the number and structure of subgroups differ by school or sex, and (c) investigate whether aggressive-victims differ from all other subgroups in their social and emotional functioning. Secondary analyses were conducted on baseline data from 984 seventh grade adolescents participating in a randomized controlled trial evaluating an expressive writing intervention. Latent class analysis identified four subgroups of adolescents representing predominant-aggressors, predominant-victims, aggressive-victims, and youth with limited involvement. This pattern was consistent across sex and across schools that differed in the demographics of the adolescents. The findings indicate that aggressive victims are highly similar to predominant-aggressors and do not possess any unique characteristics beyond their pattern of involvement in both aggression and victimization. Further evidence of unique differences in risk factors is needed to support prevention and intervention efforts that are tailored to meet the specific needs of aggressive-victims. Future research should consider addressing methodological limitations of the present study, such as by examining continuous indicators, including additional indices of social and emotional functioning, or investigating differential item functioning.
120

Latent Tuberculosis Infection Treatment Completion and Predictors of Noncompletion among Visa Holders in the Rural Setting

Hutton, Scott 01 January 2018 (has links)
Latent tuberculosis infection (LTBI), a product of exposure to Mycobacterium tuberculosis (Mtb), can lead to tuberculosis (TB) and further cause death if untreated. Fortunately, TB can be prevented with LTBI treatment. Targeting newly arrived visa holders for LTBI screening and treatment is an effective strategy for decreasing future TB burden. However, LTBI treatment completion rates are low, and researches had primarily focused on the nonrural U.S. setting. This study, using a retrospective cohort design under the epidemiological disease triangle framework evaluated (a) the treatment completion rates for 2 cohorts of visa holders (i.e., immigrants, N = 31 and refugees, N = 109) with LTBI residing in the rural setting using Pearson's chi-square analysis, (b) mean times on LTBI treatment using Kaplan-Meier survival analysis, and (c) predictors of time on treatment using Cox proportional hazard regression. Study findings revealed immigrants had higher treatment noncompletion rates over refugees (25.6% and 19.3%). The potential risk factors for noncompletion were being older than 24 years of age (HR = 0.18, p = 0.01). There were also significant interactions for the time on treatment between (a) being < 25 years old and visa type (HR = 0.23, p = 0.04), (b) being < 25 years and traveling longer (miles) to treatment facility (HR = 0.25, p = 0.03), or (c) being < 25 years and Mtb blood-test positive (HR = 0.35, p = 0.05). These findings suggest interventions targeting visa holders older than 24 years may increase the rate of treatment completion and decrease the future TB cases. Therefore, the study promotes social change by providing actionable, rural-population-specific information for the prioritization of visa holders at increased risk of experiencing LTBI treatment noncompletion.

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