Aalen’s additive hazards model has gained increasing attention in recently years because it model all covariate effects as time-varying. In this thesis, our goal is to explore the application of Aalen’s model in assessing treatment effect at a given time point with varying covariate effects. First, based on Aalen’s model, we utilize the direct adjustment method to obtain the adjusted survival of a treatment and comparing two direct adjusted survivals, with univariate survival data. Second, we focus on application of Aalen’s model in the setting of competing risks data, to assess treatment effect on a particular type of failure. The direct adjusted cumulative incidence curve is introduced. We further construct the confidence interval of the difference between two direct adjusted cumulative incidences, to compare two treatments on one risk.

Il presente lavoro si è proposto di indagare il concetto di razionalità limitata nel contesto delle scelte mediche. Sono stati reclutati 80 adulti, senza una storia clinica particolare a cui è stato dapprima somministrato un test virtuale che richiedeva di prendere delle decisioni su alcuni trattamenti e, successivamente, è stata somministrata una intervista semi-strutturata per approfondire il tema della scelta. I principali risultati: in primis, le persone adottano l’uso di euristiche veloci e frugali. In particolare, le persone adottano l’euristica del “Prendi il meglio” considerando, per ogni scelta, un numero limitato di caratteristiche. In secondo luogo, l'uso di euristiche è legato a una razionalità ecologica che adatta le strategie decisionali alla struttura delle informazioni disponibili del contesto ambientale. In questo contesto, se il consiglio del o le informazioni rispetto ai rischi/effetti indesiderati sono disponibili allora essi saranno sempre valutati perché sono caratteristiche fondamentali del processo di scelta. Il consiglio del medico è espressione della fiducia tra medico e paziente. La fiducia è rappresentata da segnali semplici e onesti che il medico è capace di trasmettere e questi segnali formano un canale di comunicazione tra le persone. Infine un altro risultato riguarda la comprensione del rischio associato al consumo di un farmaco che è risultato di difficile comprensione e rappresentazione. / This research aimed at applying the concept of bounded rationality in common medical choices in order to analyse the process by which laypersons make decisions in the field of health. Eighty adults, without a particular disease history were recruited and they were asked to manage both some virtual situations of medical choices and to discuss face to face about their past experiences in medical choices.Three major findings emerged. Firstly, people often use fast and frugal heuristics. In particular, people adopt the rule of the ‘take the best” considering, for each choice, a very limited number of elements to make their decisions. Secondly, the use of heuristics is related with the principle of ecological rationality in which strategies are chosen in connection with the available information of the environmental context. In this context, if “doctor’s advice” as well as “side effects information” are available, they will be always considered because they represent fundamental features of the decision making process. Doctor’s advice is expression of the trust between patient-doctor relationship. Trust is represented by simple and honest signals that the doctor communicates and these signals form an unconscious channel of communication between people. Thirdly, we found that risks associated with treatments are not easy to be conceived by laypersons. It was that people have not in mind a clear definition of the risk implied by medicines and treatment and they show, in average, a scarce interest in risk comprehension.

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.

Bakgrund: Om tio till tolv år väntas 40 % av Sveriges 500 000 familje- och ägarledda bolag att säljas enligt en uppskattning gjord av PwC år 2012. Många små och medelstora onoterade bolag kommer därför inom den närmaste tiden att behöva värderas inför försäljning. De modeller som används vid företagsvärderingar är i dagsläget inte  anpassade för mindre onoterade bolag och dess företagsspecifika risker varför författarna valde att utföra studien. Syfte: Syftet med studien är att ta fram en praktiskt användbar modell för att skatta ett mindre onoterat bolags avkastningskrav. Modellen ska ta hänsyn till de företagsspecifika risker som är kopplade till mindre onoterade bolag. Metod: Studien bygger på en kvalitativ undersökning där intervjuer med personer som dagligen arbetar med värdering av eller rådgivning för alternativt arbetar inom mindre bolag. Utifrån data insamlad från studiens intervjuer samt teorier kring ämnet har en praktiskt funktionell modell utformats för att stödja företagsvärderares arbete i praktiken. Slutsats: BRACE-modellen (Business Risk Adjusted Cost of Equity) består av två huvudkomponenter, en CAPM-premie som mäter marknadsrisken samt en företagsspecifik riskpremie. Den företagsspecifika risken hänförs till bolagets storlek och illikviditet samt kvantifieras i en poängbedömningsskala där ett mindre bolags specifika risker tas hänsyn till. / Background: In ten to twelve years, 40 % of Sweden's 500 000 family- and owner led firms will be up for sale according to an estimation done by PwC in 2012. Many small and medium sized firms will therefore need to be valued within the near future. The models and theories used in todays' business valuations are not applicable for small private firms why the authors chose to conduct this study. Purpose: The purpose of this study is to design a practically useful model in terms of assessing the owners' required rate of return in a small private firm. The model should include the firm-specific risks that are linked to private firms. Methodology: This study uses a qualitative research method where data is collected through interviews with people who on a daily basis, work with, value and advise small private firms. From the data collected through the interviews as well as theories regarding the subject the authors have designed a practical model with the intentions to support private firm valuations. Conclusion: The BRACE-model (Business Risk Adjusted Cost of Equity) consists of two main components, a CAPM-premium and a firm-specific risk premium. The firm-specific risk premium is derived from the firm's size and illiquidity and is further quantified with a point system where a small private firm's specific risks are considered.

Most farmers in South Africa use standard insurance to protect their crops against natural disasters such as hail or strong winds. However, no South African insurance contracts exist to compensate for too much or too little rain (although floods are covered), or which will pay out if temperatures were too high or too low for a certain period of time for the relevant crop. Weather derivatives - which farmers may employ to ensure crops against adverse temperatures - do exist, but these are mostly available in foreign markets in the form of Heating Degree Days contracts and Cooling Degree Day contracts and are used chiefly by energy companies. Some South African over-the-counter weather derivatives are available, but trading in these is rare and seldom used. The goal of this dissertation is to establish a pricing equation for weather derivatives specifically for use in the South African market. This equation will be derived using a similar methodology to that employed for credit default swaps. The premium derived will be designed to compensate grape farmers from losses arising from two different climatic outcomes - in this case temperature and precipitation. These derivatives will be region and crop specific and the formulation will be sufficiently flexible as to allow for further climatic possibilities (which may be added at a later stage). These weather derivative premiums will then be compared to standard crop insurance to establish economic viability of the products and recommendations will be made regarding their usage. The possibility of the simultaneous use of these derivatives and standard crop insurance for optimal crop coverage will also be explored and discussed. / Thesis (M.Com. (Risk management))--North-West University, Potchefstroom Campus, 2011.

The current international monetary system is very different from that of a few decades ago. Many of the old restrictions that had been placed on currency and capital movements between countries have fallen away in favour of a much more liberal international payment and investment system. The global financial arena is now characterized by greater currency instability, volatility and heightened financial risks. Exchange Rate risk is one of the complex topics in the economic world. Since there are so many factors in the financial market that influence a country's currency value, it becomes very risky for importers, exporters and portfolio investors to be involved in the international trade and financial markets. The purpose of this study is to gain an understanding on how the major economic indicators have an impact on the decision-making of the importers, the exporters and investors, to further influence the volatility of the Rand; and to provide various hedging and arbitraging strategies to reduce foreign exchange rate risks. The layout of the study is based on six chapters. Chapter 1 focuses on the background and scope of the study, mainly explaining the reasons, objectives and methodology of this study. An historical overview takes place in chapter 2, where a number of different exchange rate systems will be discussed. Chapter 3 reviews different exchange rate theories in order to support the empirical study in the next chapter. Chapter 4 focuses on an investigation and comparative study on how foreign investments and trade with developed countries have an impact on currency values and visa-versa. A number of management strategies for reducing exchange rate risks are introduced in chapter 5. Chapter 6 is the summary and conclusion of the research. / Thesis (M.Com. (Economics))--North-West University, Vaal Triangle Campus, 2009.

The current international monetary system is very different from that of a few decades ago. Many of the old restrictions that had been placed on currency and capital movements between countries have fallen away in favour of a much more liberal international payment and investment system. The global financial arena is now characterized by greater currency instability, volatility and heightened financial risks. Exchange Rate risk is one of the complex topics in the economic world. Since there are so many factors in the financial market that influence a country's currency value, it becomes very risky for importers, exporters and portfolio investors to be involved in the international trade and financial markets. The purpose of this study is to gain an understanding on how the major economic indicators have an impact on the decision-making of the importers, the exporters and investors, to further influence the volatility of the Rand; and to provide various hedging and arbitraging strategies to reduce foreign exchange rate risks. The layout of the study is based on six chapters. Chapter 1 focuses on the background and scope of the study, mainly explaining the reasons, objectives and methodology of this study. An historical overview takes place in chapter 2, where a number of different exchange rate systems will be discussed. Chapter 3 reviews different exchange rate theories in order to support the empirical study in the next chapter. Chapter 4 focuses on an investigation and comparative study on how foreign investments and trade with developed countries have an impact on currency values and visa-versa. A number of management strategies for reducing exchange rate risks are introduced in chapter 5. Chapter 6 is the summary and conclusion of the research. / Thesis (M.Com. (Economics))--North-West University, Vaal Triangle Campus, 2009.

Most farmers in South Africa use standard insurance to protect their crops against natural disasters such as hail or strong winds. However, no South African insurance contracts exist to compensate for too much or too little rain (although floods are covered), or which will pay out if temperatures were too high or too low for a certain period of time for the relevant crop. Weather derivatives - which farmers may employ to ensure crops against adverse temperatures - do exist, but these are mostly available in foreign markets in the form of Heating Degree Days contracts and Cooling Degree Day contracts and are used chiefly by energy companies. Some South African over-the-counter weather derivatives are available, but trading in these is rare and seldom used. The goal of this dissertation is to establish a pricing equation for weather derivatives specifically for use in the South African market. This equation will be derived using a similar methodology to that employed for credit default swaps. The premium derived will be designed to compensate grape farmers from losses arising from two different climatic outcomes - in this case temperature and precipitation. These derivatives will be region and crop specific and the formulation will be sufficiently flexible as to allow for further climatic possibilities (which may be added at a later stage). These weather derivative premiums will then be compared to standard crop insurance to establish economic viability of the products and recommendations will be made regarding their usage. The possibility of the simultaneous use of these derivatives and standard crop insurance for optimal crop coverage will also be explored and discussed. / Thesis (M.Com. (Risk management))--North-West University, Potchefstroom Campus, 2011.

Objective: The primary aim of this study was to assess patients’ preferences between radiofrequency ablation (RFA) versus hepatic resection (HR) for the treatment of small hepatocellular carcinomas (HCC). Methods: Decision analysis was performed by using probability trade-off (PTO) technique to elicit patients’ preferences and the strength of their decisions. Results: The vast majority of the study population preferred RFA over HR (70% vs. 30%, p=0.001). Their initial choice changed if 5-year survival benefit after surgery was at least 14% superior to RFA and if the 3-year disease-free survival advantage was at least 13% better than ablation. Conclusions: The results of this study suggest that fully informed cirrhotic patients would prefer RFA if diagnosed with early stage HCC even if able to undergo surgery.

The aim of this study was to evaluate risk management strategies and decision support tools that might be useful to dryland farmers in southwest Queensland to improve their decision making. This topic was chosen because there has been little previous work done to examine the sources of risk faced by farmers in that area, the practical risk management strategies employed by these farmers, or their interests in and attitudes towards risk management. This study adopted an action-learning approach to present farmers with opportunities to use various tools that might help to manage the range of risks affecting their farm management. The study was designed to test farmers’ interests in existing tools, or the potential for developing new tools, to assist dryland farmers in southwest Queensland improve their risk management. The thesis is presented in three parts including an introduction to the study and an extensive review of the relevant literature on decision making and risk management (Part I), an overview of the area in southwest Queensland where this study was focused and the various research methods used in this study (Part II). Part III comprises four chapters reporting results and presents the conclusions from the study. The thesis also reviews the advantages and disadvantages mentioned in the literature about decision support systems (DSS) in Australian agriculture and examines some programming and simulation models that can be applied to risk management in agriculture. The research methods used in this study included a literature review, interviews, focus group discussions, an ‘expert’ survey, training workshops for farmers, and evaluation techniques. The observations and reflections from the preliminary inquiries identified soil moisture management and crop choice as the critical issues concerning dryland farmers in southwest Queensland when dealing with crop production risks. Those discussions suggested possibilities for developing a decision support tool to help farmers in the study area assess their planting options. In developing the options for a decision support tool for planting decisions, a series of workshops was conducted with farmers in the study area, while some observations of farmers who attended similar workshops in adjacent areas are also reported. These workshops provided the opportunity for participants to experience some existing risk management and decision support tools. They were also designed to collect inputs to develop an appropriate decision support tool for crop planting decisions. A ‘Key to dryland planting decisions’ for farmers in southwest Queensland was developed and the personal experiences and lessons that the author has learnt through the course of this research are reported. The thesis enhances the understanding of farmers’ attitudes to risk, contemporary risk management strategies, and decision supports tools used in agriculture. This research has contributed to knowledge in the following ways. It has presented a methodological framework for doing research of this type. This study has identified the different sources of risk faced by dryland farmers in southwest Queensland and the practical risk management strategies they employ. The research has introduced those farmers to some existing risk management and decision support tools. The research has contributed more specifically to improving their management decisions by developing a decision support tool that could help dryland farmers in southwest Queensland make better informed and more appropriate planting decisions in the very uncertain and risky conditions with which they have to cope.