This dissertation aims to extend on the idea of Bollerslev (1987), estimating ARCH models with Student-t distributed errors, to estimating Stochastic Volatility (SV) models with Student-t distributed errors. It is unclear whether Gaussian distributed errors sufficiently account for the observed leptokurtosis in financial time series and hence the extension to examine Student-t distributed errors for these models. The quasi-maximum likelihood estimation approach introduced by Harvey (1989) and the conventional Kalman filter technique are described so that the SV model with Gaussian distributed errors and SV model with Student-t distributed errors can be estimated. Estimation of GARCH (1,1) models is also described using the method maximum likelihood. The empirical study estimated four models using data on four different share return series and one index return, namely: Anglo American, BHP, FirstRand, Standard Bank Group and JSE Top 40 index. The GARCH and SV model with Student-t distributed errors both perform best on the series examined in this dissertation. The metric used to determine the best performing model was the Akaike information criterion (AIC).

Discrete phylogeographic models enable the inference of the geographic history of biological organisms along phylogenetic trees. Frequently applied in the context of epidemiological modelling, phylogeographic generalised linear models were developed to allow for the evaluation of multiple predictors of spatial diffusion. The standard phylogeographic generalised linear model formulation, however, assumes that rates of spatial diffusion are a noiseless deterministic function of the set of covariates, admitting no other unobserved sources of variation. Under a variety of simulation scenarios, we demonstrate that the lack of a term modelling stochastic noise results in high false positive rates for predictors of spatial diffusion. We further show that the false positive rate can be controlled by including a random effect term, thus allowing unobserved sources of rate variation. Finally, we apply this random effects model to three recently published datasets and contrast the results of analysing these datasets with those obtained using the standard model. Our study demonstrates the prevalence of false positive results for predictors under the standard phylogeographic model in multiple simulation scenarios and, using empirical data from the literature, highlights the importance of a model accounting for random variation.

Pathogens, such as HIV and influenza, evolve in response to the selective pressures of their host environments accumulating changes in their genomes that offer fitness benefits. This selective pressure is characterised by three properties: (1.) it is episodic, tracking changes in the adaptive immune response and drug therapy, (2.) it is directional in that only particular amino acid substitutions are favoured and (3.) it varies between genomic loci. Most previous models have ignored or inadequately addressed some of these phenomena. This work extends recent approaches to modelling episodic directional selection acting on protein-coding sequences. We use inference techniques within the topic model framework to identify loci evolving under natural selection. A notable example of such techniques are the variational Bayesian methods. We show that our approach performs well in terms of specificity and power, and demonstrate its utility by applying it to some real datasets of HIV sequences.

Social networking sites usage has shown a meteoric rise over the past decade. Social networking sites survive and thrive based on the information that users disclose. The willingness of users to disclose their information lies at the core and is the driving force of the economies of these sites. This study proposed and tested an integrated theoretical framework for self-disclosure on social networking sites. Drawing from three different theoretical perspectives viz. self-congruency theory, privacy calculus theory, and extension of unified theory of acceptance and use of technology (UTAUT2), a research model was formulated. The model was tested using survey data of 380 university students. Facebook was used as a prototype for this research. This study examined the effects of the variables emanating from the three different theoretical perspectives mentioned above on the attitudinal, intentional, and behavioral aspects of self-disclosure on social networking sites. Further, the effects of self-congruency and perceived control on trust in social networking sites and its members were evaluated. The contributions to theory and practical implications of the findings are discussed.

With rapid advance of information technology (IT), computer-based gaming has flourished for decades. Gaming becomes a part of modern culture, especially among emerging digital generations. In addition to the entertaining purpose, attempts are made to use games for serious purpose, such as education and training. With the genuine characteristics that bring enjoyment, engagement, and context, games are considered good tools for business education and training that support or even may substitute the traditional learning methods. However, there is a dearth of research with regards to the comprehensive view of how people can learn business topics through serious games and transfer the value of business games to the work practices. To fill the gap, this dissertation research focuses on the use of serious games in business education and training. In Study I, the two main elements of serious games, namely seriousness and playfulness, and how these elements play roles in game-based learning process, are investigated. From two SEM (Structural Equation Model) analyses of quantitative data from 190 MBA students who have experienced business simulation games, seriousness and playfulness are shown to explain significant parts of the game-based learning process with several antecedents. In addition, Study II investigates the potentially transferrable values of business simulation games to the business practices based on the qualitative data from 43 business professionals who have experienced various business simulation games in their Professional MBA program. The result of analyzing the business professionals arguments in Toulmins framework, various values of serious games in business practice are found. Overall, this dissertation research contributes in providing fundamental insights for future studies regarding the use of serious games in business education and training context. Also, the findings from the research provide implications to the practitioners who consider using serious games in business.

This dissertation investigates the topic of scholarship in the Information Systems (IS) discipline through a series of three papers. The papers, presented in Chapters 2, 3, and 4, each delve into a specific chronological period of IS scholarship which are delineated into the past, present, and future. Chapter 2 elucidates the IS disciplines past by categorizing the entire corpus of extant research in the Association of Information Systems Senior Scholars Basket of eight journals. Clusters derived from these mainstream journal publications represent a thematic identity of the IS discipline. After analyzing the corpus altogether, further analysis segments the corpus into shorter, 5-year periods to illuminate the historical evolution of the themes. Lastly, interpretations of the trends and a recommendation to curate an IS Body of Knowledge are discussed. Chapter 3 surveys business school deans and IS academics eliciting their present social representations of the IS discipline. It then seeks the two groups feedback regarding their level of agreement with concerns attributed to the IS discipline as summarized in Ives and Adams (2012). Group responses are evaluated independently and are juxtaposed for between-group analysis. Then, additional concerns are gathered to ensure the full range of issues are represented. Network topic maps illustrate the findings, and interpretations are discussed. Group differences suggest that IS academics are more critical of the IS discipline than business school deans. In Chapter 4, an alternative research approach is offered for conducting future scholarship efforts in the IS discipline. A framework that organizes discourse on the emergent crowdsourced research genre is constructed. Prior to building the framework, a crowdsourcing process model is developed to conceptualize how problems and outcomes interact with the crowdsourcing process. The internal process components include task, governance, people, and technology. Then, the crowdsourcing process model is applied to eight general research process phases beginning with the idea generation phase and concluding with the apply results phase. Implementation of the crowdsourced research framework expounds phase-specific implications as well as other ubiquitous implications of the research process. The findings are discussed, and future directions for the IS crowd are suggested.

A general lack of timely and suitable decision-making information remained a challenge in tertiary education institutions in South Africa for many years. A design science research study was conducted and dashboard prototypes were iteratively designed and developed in the real environment to investigate how dashboards can be applied to overcome the shortcoming. The study contributes in the area of dashboard frameworks for tertiary education institutions and in the design science research of dashboards in the discipline of business process monitoring (BPM) or business intelligence (BI). The framework proposes conceptual- and design elements, a design- and development process and was proven through theory-linked research. / Thesis (PhD)--University of Pretoria,2015. / tm2015 / Information Science / Unrestricted

The debate around the perpetual nature of endowment funds from the perspective of current versus future obligations is a major problem that I would like to address in two ways: (i) a macro-level treatment of the simultaneous asset allocation and spending rate with subsistence levels (analogous to the habit formation concept); and (ii) a micro-level analysis of one part of the endowment portfolio with a particular emphasis on the currency hedging decision. The purpose of the third chapter is to illustrate the significance of joint determination of appropriate asset allocation and spending rate decisions, and to describe the behavior of the endowment fund portfolio under certain modeling assumptions, including a sensitivity analysis that evaluates, in particular, the relationship between the spending rate and stock allocation over an extended period of time by changing the values of certain parameters in the model. The fourth chapter tackles the issue of international diversification from the point of view of active currency hedging. The ability to control risk with the possibility of return enhancement is the main reason why institutional investors such as university endowments should worry about the international diversification of investment portfolios. I have concentrated on an area, which has been overlooked by endowment funds for a long time. That is, the introduction of currency hedging in the context of an international portfolio and the provision of some behavioral considerations: first, implicitly, in the framework of the traditional expected utility maximization and then, explicitly, in the disappointment-averse functional context. In both chapters, the discussion is heavily based on the specification of the utility function; i.e., habit formation through the use of a subsistence level in the case of asset allocation and spending rate determination, and behavioral/agency-related formulation of various aversion parameters in the international portfolio management chapter.

Tech Culture is a local startup company that has a very creative idea in the network security management area. The two founders have a very strong startup for their business but encounter some problems during the expansion of their business. This thesis is to analyze their business model using effectuation theories to make sure the business model fits the current economic development. Then, start using various business theories to correctly define and analyze their problems. At the end, some theory-driven suggestions are given to Tech Culture for its future development.

Information Systems Design Science (ISDS) as a research community is limited by a small number of research frameworks with considerable influence. The small triad of influential ISDS research, consisting of Walls, et al (1992), March and Smith (1995), and Hevner et al (2004) have primarily limited ISDS research to the positivist paradigm and the IT artifact. In contrast, Herbert Simons intentions for design science never had such restrictions and intended a broader perspective. This dissertation explores Simons intentions for design science, the Simonian stream of thought that includes The Sciences of the Artificial, as well as much of his most notable research, and offers an informed view of design science in the tradition of Rortyian neopragmatism. Using this new lens of design science, a Bhaskarian critical realist treatment of human artifacts is also developed. Collectively, a Rortyian neopragmatist treatment for design science, and a Bhaskarian critical realist treatment of human artifacts are used as a lens to augment the Walls et al (1992) framework for Information Systems Design Theories (ISDT). An example of how to apply this lens is accomplished in Paper 2 of the dissertation. The ISDS lens is applied to the topic of Enterprise Architecture (EA). EA as vehicle for IS Alignment is well defined in terms of frameworks, artifacts, and methodology. However little is understood with respect to the discipline and practice of EA. Seeking to advance our understanding of effective vehicles for IS alignment, this research examines EA as an alignment practice and how it attempts to realize alignment. Specifically, we address the following question: How does EA manifest itself in organizations? This research employs an interpretivist epistemology in a manner quite distinct from ISDS research and thus provides contributions to academia in terms of methodology and insight on EA, and for practitioners who wish to mature an EA practice in their organization. Some of the main concepts discovered in the empirical study in Paper 2 are used to develop a practitioner-oriented framework for EA practice in Paper 3.