Short selling, and its informational role in the formation of stock prices have been the epicenter of prior literature. Is there a relationship between short selling and abnormal returns? While numerous studies found a negative relationship, researchers do not unanimously agree on the existence, nor the strength, of this relationship. Using net short positions extracted from the registry of the FI for stocks listed in the OMX Stockholm 30 Exchange from January 2017 to December 2020, we examine this relationship exclusively in Sweden. The results have been scrutinized via regression analysis to verify if there is any significant relationship between the announcements of total net short positions and the non-adjusted, as well as the risk-adjusted abnormal returns. We did not find enough evidence to validate previous studies that supported the notion that heavily shorted stocks generate negative abnormal returns for the long buyers. There was a perceptible increase in both risk-adjusted and non-adjusted abnormal returns within a three-day window after the announcement of a short position. Yet, the value was merely zero, inferring that a higher level of short interest does not lead to negative stock returns.

This paper firstly constructed an order-driven market probability model of informed trading to analyze the correlation between informed trade and return of assets and the trade-price effect. Secondly, using the probability model of informed trading, we constructed a probability model of arbitrage trading in order-driven call market, which could analyze the stabilization fund and the arbitrage trade, to investigate whether the government¡¦s interference measures were necessary and whether the intervened timepoints conformed to the set-up spirit of the stabilization fund¡Xto intervene while falling and not to while rising. Finally, we set up a ratio empirical model of informed trading which could analyze the intraday trade scale of each trade section of informed traders and uninformed traders, to analyze the change of intraday trade scale of each type of investors while trade frequency changed to explore the factors of market performance. The main results are as follows respectively: Regarding the correlation analysis of informed trading and return of assets and trade-price effect, we found that (1) in the short-term (intraday, day) there was no relationship between probability of informed trading and return of assets, whereas in the mid-term probability of informed trading was correlated with return of assets although the influence impact was not as high as prior researches (Hasbrouck (1991a, b), Glosten and Harris (1988)) expected. (2) The intraday probability of informed trading of good news days was obviously higher than that of bad news days, which indicated that unbalanced buy-sell informed trade phenomenon existed in the market. Regarding the investigation of whether the intervened timepoints of stabilization fund conformed to the set-up spirit of the stabilization fund¡Xto intervene while falling and not to while rising, the main results are: (1) the individual stocks intervened by the stabilization fund had slightly smaller volatility, slightly worse efficiency, better returns and significantly larger liquidity. (2) There was no significant difference in the probability of arbitrage trading between the targets intervened by the stabilization fund and the other companies, nor in the performance (including volatility, efficiency, liquidity and return) between both. (3) The stabilization fund and arbitragers tended to conduct transactions in the opening period, which corresponds with the proposition of Schwartz (1988). (4) We also found that compared with other arbitrage trade, the trade of the stabilization fund was more correlated with the price up-down of the market, but not with that of individual stocks. In the analysis of the intraday trade scale change of each type of investors while trade frequency changed, the main findings are: (1) the slowdown of trade frequency caused smaller intraday trade ratio and worse performance in the opening, but it increased the intraday trade ratio and performance of the closing period, which was especially significant in the high-liquidity companies. (2) The increase of trade frequency could raise the liquidity of the high-liquidity and middle-liquidity companies. As to the low-liquidity companies, although the increase of trade frequency increased the liquidity, it raised their volatility and decreased their price finding speed. The main contributions of this paper¡¦s models are indicated as follows. Regarding a probability model of informed trade: first, it improves the prior ones by bringing the order-driven call market model; second, the addition of informed traders¡¦ possibility to use limit order in the model set-up better corresponds to the real market; third, the model can calculate the probability of informed trading of intraday trade section and thus can analyze the intraday and intraweek behavior or phenomenon of informed traders and the market; fourth, the model estimates the probability of informed trading using trade data, not order data, and thus avoids the probability of informed trade estimation error caused by order trade risk; fifth, the model calculates the probability of informed trade of individual stock after separating good and bad news and thus can analyze buy-sell informed trade behavior. Regarding the probability model of arbitrage trading, it provides a method to analyze whether self-stabilization mechanism-arbitrage trade exists in the market to investigate on the necessity of the stabilization fund and its intraday trade behavior. Finally, regarding the ratio empirical model of informed trading, since this paper calculated the section informed and uninformed trade ratio by simulating uninformed traders¡¦ intraday trade strategy and by extracting the ratio of the trade volume variation of intraday trade section explained by uninformed traders¡¦ intraday behavior variation using regression analysis, it can avoid the deficiency that every trade volume was regarded as from a single trader in the prior order empirical model of informed trading.

根據Easley, Kiefer, O’Hara and Paperman (1996)所發展的模型，我們可以對台灣證券交易所上市的股票進行訊息交易的研究。我們的結果顯示，交易越活絡的股票含有訊息交易的機率越低；而這與Easley, Kiefer, O’Hara and Paperman的研究結果一致；換句話說，紐約證券交易所與台灣證券交易所的股票對於訊息交易都有類似的特性。因此，根據研究結果，沒有訊息的投資人應該多去交易較活絡或交易量較大的股票，因為這些股票含有訊息交易的機率較低。 / Following the empirical model developed by Easley, Kiefer, O’Hara and Paperman (1996), we have investigated the information content of the stocks on the TSEC. Our result reveals that more liquid stocks have the lower risk of informed trade than do less liquid stocks and this is basically consistent with the finding of Easley, Kiefer, O’Hara and Paperman. Stocks on the NYSE and the TSEC have similar characteristics of informed trade. Therefore, for uninformed traders, it is better for them to trade stocks which are more liquid and have higher trading volume.

The thesis is focused on solving the Sokoban game using artificial intelligence algorithms. The first part of the thesis describes the Sokoban game, state space and selected state space search methods. In the second part selected methods were implemented and graphic user interface was created in the Python environment. Comparative experiments were executed in the final part.

This thesis presents the theme of low political awareness of adult citizens in the Czech Republic from the perspective of public policy. Low level of political awareness is conceived as a major reason that voters are not able to vote according to their real interests. The focus is on whether the problem is a topic that public policy should pursue and whether it is possible to find a public policy tools to deal with it. It is mainly based on the three-dimensional model of political sophistication, Evert Vedung's concept of public policy instruments, the concept of the correct voting and ideas of participatory democracy. Despite the fact that the given issue bears the hallmarks of an ideal problem for public policy and we can find some tools that could improve the current situation, there are broader factors that hinder their operations. These include the impact of previous undemocratic regime or the behavior of politicians. Such barriers are closely related to the way of human thinking and can be removed only with difficulty.