Zugl.: Hamburg, Universiẗat, Diss., 2009.

Typescript (photocopy). / Digitized by Kansas Correctional Industries

This study investigates how outliers of different magnitude impact the robustness of the twosample t-test. A simulation study approach is used to analyze the behavior of type I error rates when outliers are added to generated data. Outliers may distort parameter estimates such as the mean and variance and cause misleading test results. Previous research has shown that Welch’s ttest performs better than the traditional Student’s t-test when group variances are unequal. Therefore these two alternative statistics are compared in terms of type I error rates when outliers are added to the samples. The results show that control of type I error rates can be maintained in the presence of a single outlier. Depending on the magnitude of the outlier and the sample size, there are scenarios where the t-test is robust. However, the sensitivity of the t-test is illustrated by deteriorating type I error rates when more than one outlier are included. The comparison between Welch’s t-test and Student’s t-test shows that the former is marginally more robust against outlier influence.

The current study determined if a professional development on PTSD would improve pre-service teachers’ self-efficacy for helping students with posttraumatic stress disorder (PTSD) to learn. Participants consisted of 59 college students from one large, comprehensive, Mid-Southern university who were enrolled in an education program and an educational psychology course. Using a quasi-experimental method, participants either received the PTSD professional development (treatment) or regular instruction (control group). All participants completed a measure of demographics, a pre-test measure of selfefficacy for helping students with PTSD to learn, which was further dissected into four constructs (i.e., self-efficacy for identifying students with PTSD, adapting instruction to maximize learning, creating a safe and secure environment, and finding help), and a posttest measure of the same self-efficacy items. A one-way MANOVA indicated statistically significant differences between the two groups in self-efficacy for identifying students with PTSD. Furthermore, a paired-samples t-test revealed that the treatment groups’ selfefficacy scores on all four constructs significantly improved from pre- to post-test. Information is offered to support this finding; additionally, possible reasons for nonsignificant findings are discussed.

With the emerging computing technologies and applications in the past decades, cryptography is facing tremendous challenges in its position of guarding our digital world. The advent of quantum computers is potentially going to cease the dominance of RSA and other public key algorithms based on hard problems of factorization and discrete logarithm. In order to protect the Internet at post-quantum era, great efforts have been dedicated to the design of RSA substitutions. One of them is code- based McEliece public key schemes which are immune to quantum attacks. Meanwhile, new infrastructures like Internet of Things are bringing the world enormous benefits but, due to the resource-constrained nature, require compact and still reliable cryptographic solutions. Motivated by this, many lightweight cryptographic algorithms are introduced. Nevertheless, side channel attack is still a practical threat for implementations of these new algorithms if no countermeasures are employed. In the past decades two major categories of side channel countermeasures, namely masking and hiding, have been studied to mitigate the threat of such attacks. As a masking countermeasure, Threshold Implementation becomes popular in recent years. It is sound in providing provable side channel resistance for hardware-based cryptosystems but meanwhile it also incurs significant overheads which need further optimization for constrained applications. Masking, especially for higher order masking schemes, requires low signal-to-noise ratio to be effective which can be achieved by applying hiding countermeasures. In order to evaluate side channel resistance of countermeasures, several tools have been introduced. Due to its simplicity, TVLA is being accepted by academy and industry as a one-size-fit-all leakage detection methodolgy that can be used by non-experts. However, its effectiveness can be negatively impacted by environmental factors such as temperature variations. Thus, a robust and simple evaluation method is desired. In this dissertation, we first show how differential power analysis can efficiently exploit the power consumption of a McEliece implementation to recover the private key. Then, we apply Threshold Implementation scheme in order to protect from the proposed attack. This is, to the best of our knowledge, the first time of applying Threshold Implementation in a public key cryptosystem. Next, we investigate the reduction of shares in Threshold Implementation so as to bring down its overhead for constrained applications. Our study shows that Threshold Implementation using only two shares reduces the overheads while still provides reliable first-order resistance but in the meantime it also leaks a strong second-order leakage. We also propose a hiding countermeasure, namely balanced encoding scheme based on the idea of Dual- Rail Pre-charge logic style in hardwares. We show that it is effective to mitigate the leakage and can be combined with masking schemes to achieve better resistance. Finally, we study paired t-test versus Welch's t-test in the original TVLA and show its robustness against environmental noises. We also found that using moving average in computing t statistics can detect higher-order leakage faster.

O objetivo do estudo foi investigar o construto da tarefa de múltiplas acelerações a partir de parâmetros biomecânicos de saltos verticais. 19 jogadoras da seleção brasileira adulta de basquetebol feminino realizaram o teste de múltiplas acelerações (teste T), salto vertical com contramovimento (SV) e salto vertical com contramovimento precedido de corrida (SVcorrida). Os parâmetros biomecânicos do SV foram, tempo de fase concêntrica (Tcon), pico de força de propulsão (PFP), tempo decorrido entre início da fase concêntrica e o pico de força de propulsão (TPFP), taxa de desenvolvimento de força (TDF) e impulso (I); para SVcorrida, velocidade média de aproximação (Velmédia), tempo total do movimento (Ttotal), pico de força passiva (PFPa), tempo decorrido entre início da fase de apoio e pico de força passiva (TPFPa), pico de força de propulsão (PFP), tempo decorrido entre início da fase de apoio e pico de força de propulsão (TPFPp), Load Rate (LR) e taxa de desenvolvimento de força (TDF). Para análise dos dados, inicialmente, recorreu-se a análise de componentes principais, revelando que 61,3% da variância total do SV foi explicada pelo componente predominantemente temporal (Tcon, TPFP e PFP) e 20,7% pelo componente predominantemente cinético (I e TDF); para SVcorrida, 58,7% da variância total foi explicada pelo componente predominantemente temporal (Ttotal, TPFPa, TPFPp, LR e TDF), 15,4% pelo componente predominantemente cinético (PFPa e PFP) e 12,8% pelo componente velocidade (Velmédia). Adicionalmente, foram reveladas correlações significantes de 0,55 (Tcon), -0,54 (Velmédia) e -0,49 (PFP) com o teste T, evidenciando um construto determinado pela capacidade de se gerar elevada força na fase concêntrica, reduzir o tempo de fase concêntrica e se aproximar do ponto de mudança de direção com elevada velocidade. / The main aim of the study was to investigate the multiple-acceleration task construct from vertical jumps biomechanics parameters. Nineteen female basketball players from Brazilian national team performed the multiple-acceleration test (T test), countermovement jump (VJ) and countermovement jump preceded by run (VJr). The VJ biomechanics parameters observed were: concentric phase duration (CPD), propulsion peak force (PPF), time to reach propulsion peak force (TPPF), rate of force development (RFD) and impulse (I); for VJr the parameters were mean velocity (MV), movement total duration (MTD), passive peak force (PaPF), time to reach passive peak force (TPaPF), propulsion peak force (PPF), time to reach propulsion peak force (TPpPF), load rate (LR) and rate of force development (RFD). Data were first analyzed by principal component analysis. The results showed that 61.3% of VJ variance could be explained by time factor (CPD, TPPF and PPF), and 20.7% by kinetic factor (I and RFD). To VJr, 58.7% of total variance could be explained by time factor (MTD, TPaPF, TPpPF, LR, RFD) and 15.4% by kinetic factor (PPF and PaPF) and 12.8% by velocity factor (MV). Furthermore, significant correlations were found between T test with CPD, MV and PPF (0.55, -0.54 and -0.49, respectively), revealing a T test construct related to the ability of generating high level of force in concentric phase, diminishing time of concentric phase, and to reach the change direction point with greatest possible speed.

The Texas Department of Transportation (TxDOT) uses the Texas Condition Assessment Program (TxCAP) to measure and compare the overall road maintenance conditions among its 25 districts. TxCAP combines data from three existing subsystems: the Pavement Management Information System (PMIS), which scores the condition of pavement; the Texas Maintenance Assessment Program (TxMAP), which evaluates roadside conditions; and the Texas Traffic Assessment Program (TxTAP), which evaluates the condition of signs, work zones, railroad crossings, and other traffic elements to get an overall picture of the condition of state roads. As a result, TxCAP provides a more comprehensive assessment of the interstate and non-interstate highways. However, the scores for each of the subsystems are based on data of different sample sizes, accuracy, and levels of variations, making it difficult to decide if the difference between two TxCAP score is a true difference or measurement error. Therefore, whether the use of TxCAP is an effective and consistent means to measure the TxDOT roadway maintenance conditions raises concerns and needs to be evaluated. In order to achieve this objective, statistical analyses of the system were conducted in two ways: 1) to determine whether sufficient samples are collected for each of the subsystems, and 2) to determine if the scores are statistically different from each other. A case study was conducted with a dataset covering the whole state from 2008 to 2010. The case study results show that the difference in scores between two districts are statistically significant for some of the districts and insignificant for some other districts. It is therefore recommended that TxDOT either compare the 25 districts by groups/tiers or increase the sample size of the data being collected to compare the districts as individual ones. / text

Zugl.: Hamburg, Universiẗat, Diss., 2007.

Stress and psychosomatic symptoms are an increasing problem in todays society, where adolescents are a group more exposed than others. Over the years, stress as a concept has been developed and is today linked to chronic diseases, depression and cardiovascular diseases. Many people experience long lasting, chronic stress which the body is no good at handling. Women seem to generally experience more stress than men, which can be related to the society’s view of gender. This can also be linked to how men and women handle stress, which seem to be in different ways. Sense of coherence can also be linked to stress, where higher sense of coherence correlates with lower experienced stress and lower sense of coherence with higher stress, which also can be linked with age, though there is a need for more studies on the subject to show this. The aim of this study is to investigate a possible connection between age, gender, type of education and stress. The study has a comfort selection with a total of 79 respondents, of which are 56 women and 23 men. The result of this study shows no significant difference between gender, age, type of education and stress, though there is a slight difference in the descriptive analysis. To obtain a significant result, the study selection would’ve had to be representable and a higher number of respondents would have had to be included. / Stress och psykosomatiska symtom är ett ökande problem i dagens samhälle där ungdomar är speciellt utsatta. Stress har som begrepp utvecklats under årens gång, men kopplas idag ihop till flera kroniska sjukdomar, nedstämdhet och hjärt- och kärlsjukdomar. Människor utsätts idag för långvarig, kronisk stress, vilket kroppen inte är konstruerad för. Kvinnor verkar generellt sett uppleva mer stress i vardagen än män, vilket kan kopplas till samhällets syn på kön och genus. Detta kan även kopplas till hur män och kvinnor hanterar stress, vilket verkar vara annorlunda. Ytterligare så kan känsla av sammanhang kopplas till stress, där en högre känsla av sammanhang har en samband med lägre stress och tvärt om. Forskare menar att graden av känsla av sammanhang ökar med åldern, vilket då även kan kopplas till en lägre stressnivå vid högre ålder. Dock behövs mer forskning för att fastställa detta. Syftet med studien är att undersöka om det finns ett samband mellan ålder, kön, typ av utbildning och stress. Studien har ett bekvämlighetsurval med totalt 79 respondenter, varav 56 kvinnor och 23 män. Resultatet i denna studie visar inte på någon signifikant skillnad mellan kön, ålder och utbildning i relation till stress, då endast vissa små skillnader identifieras i den deskriptiva analysen. För att kunnat få ett signifikant resultat hade studien behövt ha en annan typ av urval och ett större antal respondenter.

The thesis deals with the question whether the financial crisis caused changes in the structure of tax revenues in the EU Member States. It's necessary to specify trends in the tax mixes that helps us to determine whether the changes in the structure can be really caused by the crisis or it is EU long-term trend. The analysis focuses on indirect taxes, social contributions and direct taxes that are analyzed separately as personal income taxes and corporate income taxes. The analyzed period is the beginning of the crisis. These are mostly the changes in the turning period pre-crisis and crisis (2006 and 2007 are compared with 2008 and 2009). The analysis is performed by t-tests.