• Journal of the Korean Data and Information Science Society
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• v.20 no.5
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• pp.887-894
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• 2009

The two-stage minimum risk point estimation of mean, the probability of success in a sequence of Bernoulli trials, is considered for the case where loss is taken to be symmetrized relative squared error of estimation, plus a fixed cost per observation. First order asymptotic expansions are obtained for large sample properties of two-stage procedure. Monte Carlo simulation is carried out to obtain the expected sample size that minimizes the risk and to examine its finite sample behavior.

• The Korean Journal of Applied Statistics
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• v.29 no.4
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• pp.689-697
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• 2016

The most useful method for financial market risk management may be Value at Risk (VaR) which estimates the maximum loss amount statistically. The VaR is used as a risk measure for one industry. Many real cases estimate VaRs for many industries or nationwide industries; consequently, it is necessary to estimate the VaR for multivariate distributions when a specific portfolio is established. In this paper, the multivariate quantile vector is proposed to estimate VaR for multivariate distribution, and the Vector at Risk for multivariate space is defined based on the quantile vector. When a weight vector for a specific portfolio is given, one point among Vector at Risk could be found as the best VaR which is called as an alternative VaR. The alternative VaR proposed in this work is compared with the VaR of Morgan with bivariate and trivariate examples; in addition, some properties of the alternative VaR are also explored.

• Journal of Korean Institute of Industrial Engineers
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• v.25 no.4
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• pp.437-447
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• 1999

Previous researches on risk attitudes or on the typical utility functions have mostly focused on how the risk attitude of decision maker varies when changes are made in one or two lottery reference points such as consequence domain and magnitude of probability under assumed risk situations represented by simple lotteries. It is, however, very difficult to forecast dominant risk attitudes under risk situations which exhibit a complex combination of many reference points. In this study, twelve risk situations which a decision maker may confront in real decision-making situations were formulated by combining in various ways three reference points, that is, magnitude of probability, consequence domain, and magnitude of gain or loss. Then through a questionnaire dominant risk attitudes under every assumed risk situation were investigated, and the general shape of utility function implied by the experimental results were derived. Results of the present study show that none of the three reference points have dominant effect over the others due to complicated interaction between them, and given the twelve risk situations the observed risk attitude widely varies from strong risk taking to strong risk aversion.

• The Journal of Advanced Prosthodontics
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• v.2 no.4
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• pp.122-127
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• 2010

PURPOSE. The aim of this study was to examine the relationship between tooth loss and sub-clinical atherosclerosis in Korean adults. MATERIALS AND METHODS. The subjects were part of a cohort study conducted in Ansan city by the Korea University medical school as part of the Korean Genome project. 749 subjects over than 40 years old were evaluated. After taking panoramic radiography, the amount of tooth loss was calculated. The intima-media thickness (IMT) was assessed by using ultrasonography at the common carotid artery. Traditional cardiovascular risk factors for atherosclerosis were also evaluated. The relationship between tooth loss and the IMT was evaluated using ANOVA with Scheffe's multiple comparison method in univariate analysis. Multiple regression analysis was also performed to determine the significance between the IMT and tooth loss. RESULTS. With age, tooth loss increased, but there was no significant increase in other traditional cardiovascular risk factors. Univariate analysis revealed the IMT to be positively related with the amount of tooth loss. Regression analysis of the IMT in the anterior and posterior tooth loss revealed that only the posterior tooth loss was significantly related with the IMT at all sites of the common carotid artery (right far wall, P = .015; left far wall, P = .008; right near wall, P < .001; left near wall, P = .001). CONCLUSION. This study verified the positive relationship between the increased tooth loss at the posterior area and the accumulation of atheroma in arteries.

• Journal of the Korean GEO-environmental Society
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• v.20 no.3
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• pp.5-14
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• 2019

This study attempted to study the soil erosion dynamic in the Bagmati Basin of Nepal. In this study, an inclusive methodology that combines Revised Universal Soil Loss Equation (RUSLE) and GIS techniques was adopted to determine the distribution of soil loss in the study basin. As well, this study attempts to study the intensity of soil erosion in the seven different land use patterns in the Bagmati Basin. Soil loss is an associated phenomenon of hydrologic cycle and this dynamic phenomenon possesses threats to sustainability of basin hydrology, agriculture system, hydraulic structures in operation and overall ecosystem in a long run. Soil conservation works, and various planning and design of watersheds works demands quantification of soil loss. The results of the study in Bagmati Basin shows the total annual soil loss in the basin is 22.93 million tons with an average rate of 75.83T/ha/yr. The computed soil loss risk was divided into five classes from tolerable to severe and the spatial pattern was mapped for easy interpretation. Also, evaluation of soil loss in different land use categories shows barren area has highest rate of soil loss followed by agriculture area. This is a preliminary work and provides erosion risk scenario in the basin. The study can be further used for strategic planning of land use and hydrologic conservation works in a basin.

• The Korean Journal of Applied Statistics
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• v.26 no.6
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• pp.857-871
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• 2013

Export credit insurance is a policy tool for export growth. In the era of free trade under the governance of WTO, export credit insurance is still allowed as one of the few instruments to increase exports. This paper, using data on short-term export insurance contracts issued to foreign subsidiaries of Korean companies, calculates the expected loss per exposure by combining the effect of risk factors (credit rate of foreign importers, size of mother company, and payment period) on loss frequency and loss severity in different levels. We, applying generalized linear models (GLM), first fit loss frequency and loss severity to negative binomial and lognormal distribution, respectively, and then estimate the loss frequency rate per contract and the ratio of loss severity to coverage amount. Finally, we calculate the expected loss per exposure for each level of risk factors by combining these two rates. Based on the result of statistical analysis, we present the implication for the current premium rate of export insurance.

• Health Policy and Management
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• v.17 no.3
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• pp.68-86
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• 2007

This study was performed to explore the effect of customer satisfaction and switching barriers on customer royalties in medical services. 900 households, 1% sample were randomly selected from K city located in Kangwon province. Interview survey was performed with structured questionnaire for the entire people, 923 persons who experienced medical service utilization during one year before survey on time, september, 2002. In comparison of switching barriers by sociodemographic characteristics, lower income group and lower educated group showed the higher level of recognition level on availability of changing the service provider significantly. In terms of economic loss as one of switching barriers, the group of over aged 61, the lower income group and the lower educated group felt higher than other groups. Also, the time loss of switching barrier was recognized in 41-60 aged group and employee in service industry highly. For the perceived risk factor as another switching barrier, the high educated group showed the higher recognition level in performance risk and felt higher social risk than other groups. In analysis of customer satisfaction and loyalty levels by switching barrier components, the lower level of availability of changing the service provider and the higher level of recognition for economic and time loss, they showed the higher satisfaction and loyalty levels. In final step, multiple regression analysis showed the positive relationship between customer satisfaction, switching barrier and customer loyalties. Besides, the moderating effect of switching barrier in relationship between customer satisfaction and loyalties was significant and this results suggests that the influence of customer satisfaction to customer loyalties might be weakened in high level of recognition for switching barrier. In conclusion, perceived risk of economic and time loss as switching barrier is an important factor and should be considered in planning of marketing strategy carefully in terms of defensive marketing.

• The Korean Journal of Applied Statistics
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• v.27 no.1
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• pp.71-87
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• 2014

The Bayes premium or the net premium in the credibility theory does not reflect the underlying tail risk. In this study we examine how the tail risk measures can be utilized in determining the risk premium. First, we show that the risk measures can not only provide the proper risk loading, but also allow the insurer to avoid the wrong decision made with the Bayesian premium alone. Second, it is illustrated that the rank of the tail thickness among different conditional loss distributions does not preserve for the corresponding predictive distributions, even if they share the identical prior variable. The implication of this result is that the risk loading for a contract should be based on the risk measure of the predictive loss distribution not the conditional one.

• Journal of the Korean Data and Information Science Society
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• v.27 no.6
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• pp.1453-1463
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• 2016

The most useful financial risk measure may be VaR (Value at Risk) which estimates the maximum loss amount statistically. The VaR tends to be estimated in many industries by using transformed univariate risk including variance-covariance matrix and a specific portfolio. Hong et al. (2016) are defined the Vector at Risk based on the multivariate quantile vector. When a specific portfolio is given, one point among Vector at Risk is founded as the best VaR which is called as an alternative VaR (AVaR). In this work, AVaRs have been investigated for multivariate normal distributions with many kinds of variance-covariance matrix and various portfolio weight vectors, and compared with VaRs. It has been found that the AVaR has smaller values than VaR. Some properties of AVaR are derived and discussed with these characteristics.

• Journal of Positioning, Navigation, and Timing
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• v.9 no.3
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• pp.285-292
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• 2020

This paper introduces a new computational efficient Dilution of Precision (DOP)-based landmark exclusion method while ensuring the safety of the LiDAR-based navigation system that uses an innovation-based Nearest-Neighbor (NN) Data Association (DA) process. The NN DA process finds a correct landmark association hypothesis among all potential landmark permutations using Kalman filter innovation vectors. This makes the computational load increases exponentially as the number of landmarks increases. In this paper, we thus exclude landmarks by introducing DOP that quantifies the geometric distribution of landmarks as a way to minimize the loss of integrity performance that can occur by reducing landmarks. The number of landmarks to be excluded is set as the maximum number that can satisfy the integrity risk requirement. For the verification of the method, we developed a simulator that can analyze integrity risk according to the landmark number and its geometric distribution. Based on the simulation, we analyzed the relationship between DOP and integrity risk of the DA process by excluding each landmark. The results showed a tendency to minimize the loss of integrity performance when excluding landmarks with poor DOP. The developed method opens the possibility of assuring the safety risk of the Lidar-based navigation system in real-time applications by reducing a substantial amount of computational load.