O efeito disposição, originalmente proposto por Shefrin e Statman (1985), preconiza que os investidores tendem a vender ações com lucro em um curto período de tempo e manter ações com prejuízo por um longo período de tempo. A despeito da ampla gama de evidências sobre o assunto, as razões que levariam os investidores a manifestar esse viés comportamental ainda é motivo de uma controvérsia importante entre motivações racionais e comportamentais. Neste trabalho, o objetivo foi testar duas motivações comportamentais concorrentes para explicar o efeito disposição: a teoria perspectiva e o viés da reversão à média. Para cumprir esse objetivo, foi feita uma análise das transações mensais de compra e venda de uma amostra de 51 fundos de investimento em ações brasileiros, no período de 2002 a 2008. A análise envolveu a estimação de dois modelos de regressão de variável dependente qualitativa. O primeiro consistiu em um modelo logit binário cujo propósito foi determinar a probabilidade de um gestor realizar um ganho ou uma perda de capital em razão de variáveis de retorno das ações. O segundo foi um modelo logit ordenado cujo objetivo foi verificar a existência de uma relação entre as variáveis de retorno e o volume monetário vendido das ações. Em ambos os modelos, os parâmetros estimados para as variáveis de retorno das ações foram interpretados como um coeficiente de disposição, sendo que a proposição desse coeficiente consistiu na principal contribuição da pesquisa. Os resultados dos modelos estimados trouxeram evidências de que a teoria perspectiva parece permear o processo decisório dos gestores dos fundos analisados. Já no caso da hipótese de que o efeito disposição é decorrente do viés da reversão à média, não foi possível corroborá-la com base nos resultados aqui relatados. / The disposition effect, originally proposed by Shefrin and Statman (1985), predicts that investors tend to sell winning stocks too soon and ride losing stocks too long. Despite the wide range of research evidence about this issue, the reasons that lead investors to act this way is still subject to much controversy between rational and behavioral explanations. In this thesis, the main goal was to test two competing behavioral motivations to justify the disposition effect: prospect theory and mean reversion bias. To achieve this goal, an analysis of monthly transactions for a sample of 51 Brazilian stock funds from 2002 to 2008 was conducted. The analysis involved the estimation of two regression models with qualitative dependent variable. The first one consisted of a binary logit model whose purpose was to set the probability of a manager to realize a capital gain or loss as a function of the stock return. The second one was an ordered logit model whose objective was to verify the existence of a relationship between stock returns and the monetary volume sold. In both models, the estimated parameters for the stock return variables were interpreted as a disposition coefficient and the proposition of this coefficient was the main contribution of the research. The results of the estimated models brought evidence that prospect theory seems to guide the decision making process of the managers of the analyzed funds. The hypothesis that the disposition effect is due to mean reversion bias could not be confirmed based on the results reported here.

O cenário do ciclo de implantação de hotéis apresenta características diferenciadas em relação aos demais empreendimentos de real estate. Dentre essas, se destaca a presença de diversos stakeholders capazes de influenciar de forma direta na configuração do empreendimento. Outra característica é a forte concentração dos processos de suprimento, em particular no final de sua fase de implantação, devido à necessidade de disponibilizar os insumos específicos dessa tipologia de empreendimento, necessários a sua entrada em operação. Esse cenário diferenciado traz ao sistema de gerenciamento de suprimentos do empreendimento demandas não usuais em outros tipos de empreendimentos de real estate, tais como: [1] um acurado processo de controle da baseline do empreendimento, [2] um abrangente processo de controle de escopo dos diversos fornecedores envolvidos, [3] necessidade de uma estreita coordenação da logística de implantação e operacionalização do empreendimento, em particular na área de suprimento. Nesse cenário, o objetivo da dissertação é apresentar diretrizes para os processos de gerenciamento da logística na implantação de hotéis, como parte integrante dos processos do gerenciamento do empreendimento, com foco naqueles aspectos que diferenciam os hotéis dos demais empreendimentos de real estate. O trabalho descreve os resultados dos levantamentos de campo sobre o escopo da implantação de hotéis, com a finalidade de identificar as necessidades desse ciclo. Estes dados, juntamente com uma análise dos processos de gerenciamento de suprimentos versus os requisitos de implantação já mencionados, permitiram estruturar diretrizes para ao gerenciamento dos processos logísticos diante das características da implantação de hotéis. A conclusão desse trabalho é a necessidade de recorrer a processos, que embora típicos do gerenciamento de empreendimentos, não são usuais na área de Gestão de Suprimentos, tais como: (1) processos de controle de escopo, (2) controle de configuração (de escopo e da baseline) e (3) controle de interfaces, aplicados em particular para a gestão da logística envolvida na implantação e operacionalização de hotéis. / The cycle of implantation of hotels is different among others real estate enterprises. There are many stakeholders capable to influence directly in the configuration of the hotel. Another characteristic is the strong concentration of the procurement processes, most in the end of the phase of implantation, due to necessity of the cycle of operation. This differentiated scene brings to the procurement management not usual demands in others real estate enterprises, such as: [1] a strong control of baseline, 2] an strong control process with involved suppliers, 3] necessity to see the needs of operation cycle during de implantation cycle. The objective of the research is to propose guidelines for the processes of the logistic in the implantation of hotels, as an integrant of the processes of management of the enterprise, with focus in those aspects that differentiate the hotels of others real estate enterprises. The research describes the results of the field surveys on the target of the implantation of hotels, with the purpose to identify the necessities of this cycle. These data, together with an analysis of the processes of procurement management versus the requirements of implantation, allowed structuralizing the guidelines for the logistic process. The conclusion of this research is the necessity to appeal the processes, that even so typical of the management of enterprises, are not usual in the area of procurement management, such as: (1) processes of scope control, (2) configuration control (baseline) and (3) control of interfaces, applied in particular for the logistic management of involved in the implantation and the of hotels operation.

Background: Preterm birth is one of the leading causes of perinatal mortality and morbidity and poses extensive economic liability. The rate of preterm births globally is approximately 11.1%, and in the US, the preterm birth rate has been estimated to be 12-13%. Folate and B12 requirements increase during pregnancy as a result of increased cell division to accommodate maternal and fetal growth; inadequate levels can result in placental abnormalities and thus present implications for preterm birth. Objective: To investigate the association between red blood cell (RBC) folate and B12 concentrations with the risk of preterm birth. Methods: Study participants were recruited from Tampa General Hospital between January 2011 and May 2013. Women with a singleton delivery occurring less than 37 weeks gestation were classified as cases and those with a singleton delivery occurring between 37 and 42 weeks gestation were classified as controls. The study had a final sample size of 227 women, including 36 cases and 191 controls. Maternal blood was collected in order to measure folate and B12 concentrations. The association between folate/B12 and preterm birth was assessed using logistic regression; odds ratio (OR), 95% confidence interval (CI) and p values are reported. A power analysis was also performed using the available sample as well as imputation for missing values in the B12 variable. Results: Although not statistically significant, the mean concentration of folate and B12 levels were higher in the cases than in the controls, 894 ± 158.1 vs. 869.2 ± 169.6 and 245.2 ± 102.2 vs 238.3 ± 81.5, respectively. No significant associations were found between folate or B12 and the risk of preterm birth. Conclusions: This study did not detect a significant association between folate or B12 and preterm birth; however, due to the small sample size this analysis was underpowered. Additional studies are needed, preferably using a randomized control study design, in order to elucidate the relationship between folate/B12 and preterm births.

The development of flexible and interpretable statistical methods is necessary in order to provide appropriate risk assessment measures for extreme events and natural disasters. In this thesis, we address this challenge by contributing to the developing research field of Extreme-Value Theory. We initially study the performance of existing parametric and non-parametric estimators of extremal dependence for multivariate maxima. As the dimensionality increases, non-parametric estimators are more flexible than parametric methods but present some loss in efficiency that we quantify under various scenarios. We introduce a statistical tool which imposes the required shape constraints on non-parametric estimators in high dimensions, significantly improving their performance. Furthermore, by embedding the tree-based max-stable nested logistic distribution in the Bayesian framework, we develop a statistical algorithm that identifies the most likely tree structures representing the data's extremal dependence using the reversible jump Monte Carlo Markov Chain method. A mixture of these trees is then used for uncertainty assessment in prediction through Bayesian model averaging. The computational complexity of full likelihood inference is significantly decreased by deriving a recursive formula for the nested logistic model likelihood. The algorithm performance is verified through simulation experiments which also compare different likelihood procedures. Finally, we extend the nested logistic representation to the spatial framework in order to jointly model multivariate variables collected across a spatial region. This situation emerges often in environmental applications but is not often considered in the current literature. Simulation experiments show that the new class of multivariate max-stable processes is able to detect both the cross and inner spatial dependence of a number of extreme variables at a relatively low computational cost, thanks to its Bayesian hierarchical representation. These innovative methods and models are implemented to study the concentration maxima of various air pollutants and how these are related to extreme weather conditions for a number of sites in California, one of the most populated and polluted states of the US. As a result, we provide comprehensive measures of air quality that can be used by communities and policymakers worldwide to better assess and manage the health, environmental and financial impacts of air pollution extremes.

Klarna uses a logistic regression to estimate the probability that an e-store customer will default on its given credit. The logistic regression is a linear statistical model which cannot detect non-linearities in the data. The aim of this project has been to develop a program which can be used to find suitable non-linear interaction-variables. This can be achieved using a Restricted Boltzmann Machine, an unsupervised neural network, whose hidden nodes can be used to model the distribution of the data. By using the hidden nodes as new variables in the logistic regression it is possible to see which nodes that have the greatest impact on the probability of default estimates. The contents of the hidden nodes, corresponding to different parts of the data distribution, can be used to find suitable interaction-variables which will allow the modelling of non-linearities. It was possible to find the data distribution using the Restricted Boltzmann Machine and adding its hidden nodes to the logistic regression improved the model's ability to predict the probability of default. The hidden nodes could be used to create interaction-variables which improve Klarna's internal models used for credit risk estimates. / Klarna använder en logistisk regression för att estimera sannolikheten att en e-handelskund inte kommer att betala sina fakturor efter att ha givits kredit. Den logistiska regressionen är en linjär modell och kan därför inte upptäcka icke-linjäriteter i datan. Målet med detta projekt har varit att utveckla ett program som kan användas för att hitta lämpliga icke-linjära interaktionsvariabler. Genom att införa dessa i den logistiska regressionen blir det möjligt att upptäcka icke-linjäriteter i datan och därmed förbättra sannolikhetsestimaten. Det utvecklade programmet använder Restricted Boltzmann Machines, en typ av oövervakat neuralt nätverk, vars dolda noder kan användas för att hitta datans distribution. Genom att använda de dolda noderna i den logistiska regressionen är det möjligt att se vilka delar av distributionen som är viktigast i sannolikhetsestimaten. Innehållet i de dolda noderna, som motsvarar olika delar av datadistributionen, kan användas för att hitta lämpliga interaktionsvariabler. Det var möjligt att hitta datans distribution genom att använda en Restricted Boltzmann Machine och dess dolda noder förbättrade sannolikhetsestimaten från den logistiska regressionen. De dolda noderna kunde användas för att skapa interaktionsvariabler som förbättrar Klarnas interna kreditriskmodeller.

The persistence rate in online classes remains significantly lower than in comparable face-to-face classes. There is a lack of research on strategies to help learners persist in online classes. The purpose of this study was to investigate the relationship between face-to-face orientations, instructor verbal immediacy behaviors, and persistence in online classes. It also explored the relationship between verbal immediacy and student satisfaction. Due to the disagreement in the literature, this study also investigated the relationship between student demographic variables, grade point average, and persistence. This quantitative study combined both causal-comparative and correlational research methods. The study took place at a community college in the southeastern United States. The participants were 171 students enrolled in online classes selected for inclusion in the study using a purposive sampling method. Students were invited to attend a face-to-face orientation prior to the start of the semester. Prior to the end of the course, students were invited to complete a survey consisting of modified versions of Gorham’s (1988) Verbal Immediacy Scale and the college’s Student Perception of Instruction survey. At the end of the semester, demographic and course completion data were collected from the college’s student information system. A chi-square analysis revealed that there was not a significant relationship between orientation attendance and persistence. A Pearson correlation analysis and a linear regression analysis revealed that there was not a significant relationship between instructor verbal immediacy and persistence. A second linear regression analysis revealed a significant relationship between verbal immediacy and student satisfaction. Perceived instructor verbal immediacy explained 33% of the variance in satisfaction. A logistic regression analysis found that while GPA was a significant predictor of persistence, age, gender, and race/ethnicity were not. The results of this study suggest that online faculty should receive training on communication strategies, such as verbal immediacy behaviors. Colleges should also consider using predictor variables, such as GPA, to identify and assist at-risk students. This study was one of the first to examine the relationship between verbal immediacy and persistence in online classes. Future research should continue to investigate this topic as well as other strategies to help students persist.

The two main causes of packet corruption in wireless sensor network are multipath fading and WiFi interference. Identifying the cause of the corruption can be used to improve the reliability of the transmission. If the corruption is caused by WiFi interference, the network could change the channel to a free one. If it is caused by multipath fading, the network could reroute the traffic away from the obstacles or shorten the distance. This project proposes a new method of corruption-causes-identification for the two causes mentioned. It is an immediate online diagnostic tool for IEEE 802.15.4 packets with a retransmission mechanism. It provides a statistical boundary with a processed deviation of RSSI value and the frame symbol error rate, and also a rechecking mechanism to check the decisions. In this model, the deviation of RSSI value is measured by the estimated RSSI value of correct packets and the current detected RSSI value. The benefit of the deviation design is that the statistical model hardly needs to retrain and correct the parameters in different transmission environments. The project also discusses two rechecking mechanism methods, one employs an individual secondary classification with its own characters; the other combines the neighbor packets' features to smooththe probable errors. To investigate the performance of the "frame symbol errorrate and deviation of RSSI values"-based diagnostic tool, the evaluation parts provide a comparison of different length packets. The conclusion is that this diagnostic tool provides a correct judgment of the accuracy of packet corruption caused by multipath fading up to 98.70%, and an accuracy of up to 92.99% for the WiFi-interferenced packet corruption.

Master´s thesis deal with the study of standardization for business of buying commodities in engeneering company producing electric motors and generators. The study includes an analysis of the current state, suggestions and quantifying potential savings.

A long record of daily data is used to study the lake levels of Lake Neusiedl, a large steppe lake at the eastern border of Austria. Daily lake level changes are modeled as functions of precipitation, temperature, and wind conditions. The occurrence and the amount of daily precipitation are modeled with logistic regressions and generalized linear models.

Fundação de Amparo a Pesquisa no Estado do Rio Grande do Sul / Knowing the consumer and their attitudes at the completion of purchases is a behavior that has been studied for several decades. Based on the theory of consumer behavior this study is to spend one more contribution to academia and industry, to present the factors that influence young people to the habit of doing or not planning ahead to situations of purchase. Thus the problem of research proposed in this study was: "What are the factors that influence the act of performing and non-planned purchases planned?". For this was a descriptive study of the quantitative type, involving a survey of field of 600 respondents, a stratified sample covering the proportion of graduate students from four institutions of higher education. Was extracted from the literature review some factors that could be linked to the fact that the purchases are made in a planned or not and, therefore, could be investigated. Bearing in mind that each factor was chosen consisting of many variables realized the need to reduce the initial set of variables, but without compromising the original meaning of each factor and, therefore, appealed to the statistical technique of cluster analysis. For a better understanding of the phenomenon it was studied by logistic regression analysis applied to other variables of the previous technique, there are aspects that are related to the increased likelihood that the purchases are planned and implemented in a Nor -planned. Thus, it was found that self-esteem and age tend to increase the chance of occurring and that the purchases planned income, materialism and compulsive buying behavior increases the likelihood of non-planned purchases occur. Furthermore, no relationship was found between any of the family structure and social factors to the act of planning or not purchasing the university. How the results can not be generalized, taking into view that was conducted among a specific audience, they become further research to better understanding and deeper in this area of study. / Conhecer o consumidor e suas atitudes no momento da realização de compras é um comportamento que vem sendo estudado há várias décadas. Com base na teoria do comportamento do consumidor este estudo tem como finalidade passar mais uma contribuição para o meio acadêmico e empresarial, ao apresentar aspectos que influenciam os jovens no hábito de realizar planejamento ou não frente a situações de compra. Dessa forma, o problema de pesquisa proposto nesse estudo foi: Quais são os fatores influenciadores do ato de realizar compras planejadas e não-planejadas? . Para isso foi realizada uma pesquisa descritiva do tipo quantitativa, envolvendo um levantamento de campo de 600 respondentes, de uma amostra estratificada proporcional abrangendo os estudantes de graduação de quatro Instituições de Ensino Superior. Foi extraído da revisão de literatura alguns fatores que poderiam estar vinculados ao fato de as compras serem efetuadas de forma planejada ou não e que, por isso, mereciam ser investigados. Tendo-se em vista que cada fator escolhido era constituído por muitas variáveis, percebeu-se a necessidade de reduzir esse conjunto inicial de variáveis sem, no entanto, comprometer o significado original de cada fator e, para isso, recorreu-se a técnica estatística de análise de cluster. Para um melhor entendimento do fenômeno estudado buscou-se por meio da análise de regressão logística, aplicada às variáveis restantes da técnica anterior, verificar quais são os aspectos que estariam relacionados com o aumento da probabilidade de as compras serem executadas de forma planejada e também nãoplanejadas. Desse modo, constatou-se que a auto-estima e a idade tendem a aumentar a chance de ocorrer compras planejadas e que a renda, o materialismo e o comportamento compulsivo de compra aumentam a probabilidade de ocorrer compras não-planejadas. Além disso, não foi evidenciada relação linear alguma entre os fatores estrutura familiar e socialização ao ato de planejamento ou não de compras pelos universitários. Como os resultados obtidos não podem ser generalizados, tendo-se em vista que fora realizado junto a um público específico, tornam-se necessárias novas pesquisas para uma melhor compreensão e aprofundamento nessa área de estudo.