<div>The simulation optimization problems refer to the nonlinear optimization problems whose objective function can be evaluated through stochastic simulations. We study two significant discrete simulation optimization problems in this thesis: Ranking and Selection (R&S) and Factor Screening (FS). Both R&S and FS are the "selection" problems defined upon a finite set of candidate systems or factors. They vary mainly in their objectives: the R&S problems is to find the "best" system(s) among all alternatives; whereas the FS is to select important factors that are critical to the stochastic systems. </div><div><br></div><div>In this thesis, we develop efficient sequential procedures for these two problems. For the R&S problem, we propose fully-sequential procedures for selecting the "best" systems with a guaranteed probability of correct selection (PCS). The main features of the stated methods are: (1) a Bonferroni-free model, these procedures overcome the conservativeness of the Bonferroni correction and deliver the exact probabilistic guarantee without overshooting; (2) asymptotic optimality, these procedures achieve the lower bound of average sample size asymptotically; (3) an indifference-zone-flexible formulation, these procedures bridge the gap between the indifference-zone formulation and the indifference-zone-free formulation so that the indifference-zone parameter is not indispensable but could be helpful if provided. We establish the validity and asymptotic efficiency for the proposed procedure and conduct numerical studies to investigates the performance under multiple configurations.</div><div><br></div><div>We also consider the multi-objective R&S (MOR&S) problem. To the best of our knowledge, the procedure proposed is the first frequentist approach for MOR&S. These procedures identify the Pareto front with a guaranteed probability of correct selection (PCS). In particular, these procedures are fully sequential using the test statistics built upon the Generalized Sequential Probability Ratio Test (GSPRT). The main features are: 1) an objective-dimension-free model, the performance of these procedures do not deteriorate as the number of objectives increases, and achieve the same efficiency as KN family procedures for single-objective ranking and selection problem; 2) an indifference-zone-flexible formulation, the new methods eliminate the necessity of indifference-zone parameter while makes use of the indifference-zone information if provided. A numerical evaluation demonstrates the validity efficiency of the new procedure.</div><div><br></div><div>For the FS problem, our objective is to identify important factors for simulation experiments with controlled Family-Wise Error Rate. We assume a Multi-Objective first-order linear model where the responses follow a multivariate normal distribution. We offer three fully-sequential procedures: Sum Intersection Procedure (SUMIP), Sort Intersection Procedure (SORTIP), and Mixed Intersection procedure (MIP). SUMIP uses the Bonferroni correction to adjust for multiple comparisons; SORTIP uses the Holms procedure to overcome the conservative of the Bonferroni method, and MIP combines both SUMIP and SORTIP to work efficiently in the parallel computing environment. Numerical studies are provided to demonstrate the validity and efficiency, and a case study is presented.</div>

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<p>In this thesis, we have analyzed the ex-dividend stock price behavior in the London Stock Exchange to see if the stock prices really drop by the same amount as the dividend on the ex-dividend day. Our sample data covers 80 FTSE100 companies of the London stock exchange for the period 2001 to 2006.</p><p>To answer the research question: Do returns on the London Stock Exchange act in accordance with the efficient market hypothesis on the ex-dividend day? We used a deductive approach and test four hypothesis. The study was carried out by comparing the actual value of the raw price ratio, market adjusted price ratio, raw price drop and market adjusted price drop to their theoretical values. The difference was tested for significance using the one sample t-test.</p><p>The results showed that there are significant differences in the observed figures from their theoretical or expected values. The observed raw price ratio is higher than the expected value of 1, implying that the stock price on the ex-dividend day drops by an amount that is lower than the dividend paid. Similarly, the market adjusted raw price ratio is also higher than the expected value of 1. The raw price drop and market adjusted price drop are lower than the dividend yield, indicating again that the stock price drops by an amount that is lower than the dividend paid.</p><p>Our results indicated that the null hypotheses stated are rejected since the drop in the stock prices is not equal to the amount of the dividend on the ex-dividend day.</p>

Thomas Marill. / "October 30, 1956." "This report is based on a thesis submitted to the Department of Economics and Social Science, M.I.T., in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Psychology, June 1956." / Bibliography: p. 73. / Army Signal Corps Contract DA36-039-sc-64637 Dept. of the Army Task No. 3-99-06-108 Project No. 3-99-00-100

Along the shores of the Northern hemisphere Fucus (Phaeophyceae) species are a prominent presence, providing substrate, shelter, and food for many species. Fucus evanescens, a non-indigenous species (NIS) in Sweden, and F. radicans, a recently described species that so far has only been found inside the species poor Baltic Sea, are the focus of this thesis. Interactions with enemies (e.g. predators, herbivores, parasites) have been shown to play a role in the success of NIS. The low consumption of Fucus evanescens by the generalist gastropod Littorina littorea in Sweden was found to depend on high levels of chemical defense in the introduced population, not the failure of the herbivore to recognize F. evanescens as suitable food. A survey of the relative abundance of F. radicans and F. vesiculosus and the most common associated fauna along the Swedish Bothnian Sea coast showed that F. radicans and F. vesiculosus are equally abundant throughout the range of F. radicans. The most common associated fauna were found to be more abundant on F. radicans compared to F. vesiculosus.  In Sweden, where F. radicans had lower levels of defense chemicals than F. vesiculosus, F. radicans was grazed more than F. vesiculosus in bioassays. This could, together with other factors, influence the range of F. radicans. Fucus radicans and F. vesiculosus are closely related, recently separated, and growing sympatrically, therefore, possible reproductive barriers between F. radicans and F. vesiculosus were studied. In Estonia F. radicans and F. vesiculosus reproduces at different times of the year. No such clear reproductive barrier was found between the two species in Sweden where they reproduce at the same time and fertilization success and germling survival were the same for hybrids as for F. vesiculosus. Since the high clonality of F. radicans means that the gentic diversity in F. radicans populations is low I investigated how genetic diversity translates to phenotypic diversity in nine traits. Phlorotannin levels, recovery after desiccation, and recovery after freezing showed inherited variation, while the other six traits showed no variation related to genetic diversity. Phenotypic variation in populations of F. radicans will be higher in populations with higher genetic diversity and this might be beneficial to the community. / <p>At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 3: Accepted.</p>

In this thesis, we have analyzed the ex-dividend stock price behavior in the London Stock Exchange to see if the stock prices really drop by the same amount as the dividend on the ex-dividend day. Our sample data covers 80 FTSE100 companies of the London stock exchange for the period 2001 to 2006. To answer the research question: Do returns on the London Stock Exchange act in accordance with the efficient market hypothesis on the ex-dividend day? We used a deductive approach and test four hypothesis. The study was carried out by comparing the actual value of the raw price ratio, market adjusted price ratio, raw price drop and market adjusted price drop to their theoretical values. The difference was tested for significance using the one sample t-test. The results showed that there are significant differences in the observed figures from their theoretical or expected values. The observed raw price ratio is higher than the expected value of 1, implying that the stock price on the ex-dividend day drops by an amount that is lower than the dividend paid. Similarly, the market adjusted raw price ratio is also higher than the expected value of 1. The raw price drop and market adjusted price drop are lower than the dividend yield, indicating again that the stock price drops by an amount that is lower than the dividend paid. Our results indicated that the null hypotheses stated are rejected since the drop in the stock prices is not equal to the amount of the dividend on the ex-dividend day.

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The study examines to what extent weak labor unions and an abundance of labor have a negative effect on less developed countries terms of trade, as hypothesized by Hans Singer (1950) and Rául Prebisch (1950). Using a sample from panel data for 74 less developed countries during the period 1980 – 2010 in OLS-regressions with fixed effects, I find some evidence that weak labor unions and abundance of labor is negatively correlated with the terms of trade, which could be interpreted in favor of the Prebisch-Singer hypothesis. The marginal effect of an abundance of labor also appears to have less negative impact on the terms of trade as labor unions grow stronger.

The primary purpose of this study is to test the validity of the trading range hypothesis as a basis for stock split decisions of Turkish companies. In the first part, the liquidity effects of stock splits on Turkish stocks are examined. Second, the optimal trading ranges for different-sized firms and firms with different investor bases are determined. Finally, the main empirical question of the study is analyzed by testing whether or not Turkish firms whose share prices rise above their optimal trading ranges are more likely to split their stock compared to firms whose share prices are at or below their optimal trading ranges. The empirical findings about the level of liquidity indicate that there is a slight decline in liquidity in the post-split periods. Analysis of the relationship between firm characteristics and share prices shows that firm size has a positive effect on share prices. The effect of investor base on share prices could not be identified. Finally, the estimation of the logit model utilized in the study to determine the probability of firms to split does not reveal any statistically significant result.