Omitted variable problem is a primary statistical challenge in various observational studies. Failure to control for the omitted variable bias in any regression analysis can alter the efficiency of results obtained. The purpose of this study is to compare the performance of four estimation methods (Proxy variable, Instrumental Variable, Fixed Effect, First Difference) in controlling the omitted variable problem when they are varying with time, constant over time and slightly varying with time. Results from the Monte Carlo study showed that, the prefect proxy variable estimator performed better  than the other models under all three cases. The instrument Variable estimator performed better than the Fixed Effect and First Difference estimator except in the case when the omitted variable is constant over time. Also, the Fixed Effect performed better than First Difference estimator when the omitted variable is time-invariant and vice versa when the omitted is slightly varying with time.

Authorship identification is the field of classifying a given text by its author based on the assumption that authors exhibit unique writing styles. This thesis investigates the semantic shortcomings of the vector space model by constructing a semantic kernel created from WordNet which is evaluated on the problem of authorship attribution. A multiclass SVM classifier is constructed using the one-versus-all strategy and evaluated in terms of precision, recall, accuracy and F1 scores. Results show that the use of the semantic scores from WordNet degrades the performance compared to using a linear kernel. Experiments are run to identify the best feature engineering configurations, showing that removing stopwords has a positive effect on the financial dataset Reuters while the Kaggle dataset consisting of short extracts of horror stories benefit from keeping the stopwords.

This paper proposes the basic predictive regression and Markov Regime-Switching regression to predict the excess stock returns in both US and Sweden stock markets. The analysis shows that the Markov Regime-Switching regression models out perform the linear ones in out-of-sample forecasting, which is due to the fact that the regime-switching models capture the economic expansion and recession better.

No description available.

Today in a modern society the pace is high and the need for flexibility and mobilityis big. Despite the increasing access and great digital solutions for online-meetings,the need for short distance transportation remains. With an increasing number ofeasy-to-use mobile applications, the many offered solutions for personal transporta-tion have in the last few years expanded. Besides the effect of an increasing pressureof road space, the pressure on the transportation solutions has escalated. This is the current situation of the company we came in contact with. Their currenttravel service provides on-demand transportation in small electric, emission free andchauffeur driven vehicles they call pods. As a step of claiming their space in thetransportation sector they are developing their application letting customers planand book a transport. For the ability to test their new booking solution this project took form. With asimulation it would be possible to test the various probabilities of a travel outcome.The aim was to develop a simulation software, simulating the events of multipletravels taking place in the system. With the simulation it would be possible to eval-uate the configuration for the booking feature, analyse how it works with the rest ofthe system and to help the company to predict how the intensity of customers in re-lations to the number of available drivers would affect the outcome of a travel request. The project covered the study of how to interpret the factors, that a transportationdirectly depends on, into events in the system and how to use historical events tocreate probabilities of the simulation outcome. The simulator software was not suc-cessful with simulating multiple rides as intended, but parts of the software could beevaluated in relation to historical events. Statistical models were built using aggre-gated events from the system. When comparing the average result of the statisticalmodels with the historical event count of the system, it resulted in an outcomewithin an acceptable range. This shows that it was possible to use aggregated his-torical events to create probabilities and that these probabilities were reliable.

Context: As most modern browsers fully support the new set of APIs called Web Components, it is crucial to investigate how developers could use them to enhance the performance and developer experience of web development. When considering this, it is fitting to investigate both the technical and practical differences between modern libraries powered by the APIs, versus traditional libraries which do not. Objectives: In this study, traditional libraries using Virtual DOM got investigated to find out which differences exist when compared to modern ones using Web Components. To find out how this next generation of front-end libraries could utilize these new APIs to improve the build process of websites. If the APIs offer alternative ways for developers to achieve better performance and developer experience. Realization:  In order to fulfill the objectives, an empirical study and a literature review were conducted. In the literature review, we investigated how a set of well-known front-end libraries technically compares to new and aspiring Web Components based libraries. In the empirical study, a new Web Components library was built from the ground up with inspiration from Vuejs. With the help of modern code styles to achieve a fresh developer experience. Results: The results of the study show that Web Components based libraries tend to be quite powerful and offer excellent all-around performance. The created library, Kirei, reflected this as it became a powerful all-around library that offers a great developer experience. It also performed equally well or even better than Vue on most benchmarks. However, Vue was better at creating new elements while Kirei excelled at updating elements. In a way, the libraries excitingly contrasted with each other. Conclusions: While Vue and React are fundamentally different from Lit-Element, Heresy, and Kirei, they are alike in some sense. Most of the differences come from how the libraries apply updates to the DOM. While Web Components based libraries patch only the dynamic parts, Virtual DOM has to diff both the dynamic and static parts. Moreover, Kirei proved to be a robust framework that could compete with Vue and React. In some benchmarks, it proved to have an upper edge in performance.

Ocean acidification is a great threat to marine ecosystems and the oceans around the poles are first in line to be affected by the increase in CO2 concentration, effectively damaging the living conditions of marine life present here. This paper analysis and discusses whether studies on the effects of ocean acidification on single species can be used to predict future changes in food web dynamics. The results indicate that by looking at effects on different physiological functions on single species, predictions on how the species in question will cope with a more acidic environment can be made. These predictions can in turn hint on possible changes in the food web. The increase in DOC as well as the shift to smaller and more toxic species of phytoplankton will prove advantageous to bacterioplankton who will play a bigger role in future carbon cycling. The toxic HAB’s could present a hazardous future for primary consumers, but especially secondary consumers. If not affected by the toxicity of the more frequent algal blooms, primary consumers will face negative consequences to the larval recruitment of copepods and shell formation of pteropods by ocean acidification. This would mean a decrease in abundance causing eutrophication and smaller amounts of food sources for fish higher up the trophic cascades, such as the endemic polar cod and the Atlantic cod. Regardless of the general scarcity of data available from these areas, all studies point to a shift in species composition. A clear indication of a future of lower diversity and ultimately an Arctic Ocean with lower ecological resilience.

A major component of the internet are websites which each have their information architecture, but more importantly, findability. This thesis focusses on the topic of findability, which is defined by Morville as “The quality of being locatable or navigable” (Morville, 2005, p. 4). Findability has become more crucial due to an increasing amount of information and time people spent on searching and gathering information. This motivation has led to the aim of investigating findability through insights into, and a delineation of, two complementary perspectives: information architecture and social informatics. Empirical evidence was collected through semi-structured interviews with design practitioners, and a literature review was conducted to provide an integrated view of findability. The STIN-model and berry-picking model provide a frame of reference which designers can use to improve the findability of their digital platforms. The most predominant suggestions based on the empirical evidence are as follows. Firstly, designers should remember that they are problem solvers and should always use methods appropriate to the problem that needs to be resolved. Secondly, designers should start with problem analysis, which should combine qualitative and quantitative methods to reach the optimal results with regards to user research. Finally, do not reinvent the wheel, make use of already existing tools that incorporate upgradeability and reusability.

No description available.

Digitalization is an important theme in Informatics research. Especially in today's digital society, people cannot live without the help of information technologies. The purpose of the study was to explore how the digitization process happened in the bicycle industry. The study was based on the background of bicycle-sharing system in Beijing and a qualitative methodology was followed. The findings show how bicycle-sharing system evolve step by step by applying advanced digital technologies. In the coming 5G era, organizations need to reconsider the situation of bicycle-sharing system and this research may give some references.