• The Korean Journal of Applied Statistics
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• v.25 no.2
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• pp.363-376
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• 2012

Excessive zeroes are often observed in ordinal categorical response variables. An ordinary ordered Probit model is not appropriate for zero-inflated data especially when there are many different sources of generating 0 observations. In this paper, we apply a two-stage zero-inflated ordered Probit (ZIOP) model which incorporate the zero-flated nature of data, propose a Bayesian analysis of a ZIOP model, and apply the method to alcohol consumption data collected by the National Bureau of Statistics, Korea. In the first stage of a ZIOP model, a Probit model is introduced to divide the non-drinkers into genuine non-drinkers who do not participate in drinking due to personal beliefs or permanent health problems and potential drinkers who did not drink at the time of the survey but have the potential to become drinkers. In the second stage, an ordered probit model is applied to drinkers that consists of zero-consumption potential drinkers and positive consumption drinkers. The analysis results show that about 30% of non-drinkers are genuine non-drinkers and hence the Korean alcohol consumption data has the feature of zero-inflated data. A study on the marginal effect of each explanatory variable shows that certain explanatory variables have effects on the genuine non-drinkers and potential drinkers in opposite directions, which may not be detected by an ordered Probit model.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.18 no.2
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• pp.179-194
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• 2020

A Bayesian approach was introduced to improve the belief of prior distributions of input parameters for the probabilistic safety assessment of radioactive waste repository. A GoldSim-based module was developed using the Markov chain Monte Carlo algorithm and implemented through GSTSPA (GoldSim Total System Performance Assessment), a GoldSim template for generic/site-specific safety assessment of the radioactive repository system. In this study, sequential Bayesian updating of prior distributions was comprehensively explained and used as a basis to conduct a reliable safety assessment of the repository. The prior distribution to three sequential posterior distributions for several selected parameters associated with nuclide transport in the fractured rock medium was updated with assumed likelihood functions. The process was demonstrated through a probabilistic safety assessment of the conceptual repository for illustrative purposes. Through this study, it was shown that insufficient observed data could enhance the belief of prior distributions for input parameter values commonly available, which are usually uncertain. This is particularly applicable for nuclide behavior in and around the repository system, which typically exhibited a long time span and wide modeling domain.

• Proceedings of the Korean Information Science Society Conference
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• 2005.07b
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• pp.433-435
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• 2005

임베디드 시스템은 다수의 디바이스를 컨트롤하여 시스템의 목적을 수행한다. 최근 임베디드 시스템의 요구사항이 증가함에 따라 하나의 임베디드 소프트웨어가 컨트롤하는 디바이스의 종류가 다양해지고 수도 증가하는 추세이다. 다수의 디바이스를 가지고 있는 임베디드 시스템에서 시스템의 신뢰도는 각 디바이스의 신뢰도에 많은 영향을 받는다. 본 논문은 임베디드 시스템의 신뢰도를 측정하기 위해서 통계적 신뢰도 측정 방법 중 한 가지인 마르코프 체인을 이용한 방법을 제안한다. 마르코프 체인은 여러 분야에서 복잡한 시스템을 단순화하여 모델링하고 과거의 변화를 토대로 미래를 예측할 수 있는 방법을 제공한다. 또한 전체 시스템의 확률을 행렬로 계측할 수 있는 방법을 가지고 있어 특정 부분의 확률이 전체 시스템의 확률에 미치는 영향을 산술적으로 계산할 수 있는 장점을 가지고 있다. 본 논문에서 제안하는 임베디드 소프트웨어 마르코프 체인은 테스트 대상 소스를 분석하여 디바이스를 컨트롤하는 루틴과 에러를 핸들링하는 루틴, 일반적인 루틴으로 나누어 각각을 상태로 정의한다. 정의한 각 상태간의 전이는 통계적으로 측정한 디바이스 신뢰도를 확률로 표현한다. 마르코프 체인을 이용하여 임베디드 시스템의 신뢰도를 측정하기 위한 시스템은 소스 분석기와 신뢰도 측정기로 나누어 설계한다. 소스 분석기는 테스트 대상이 되는 소스와 디바이스 드라이버 라이블러리 테이블을 입력으로 하고 소프트웨어의 마르코프 체인을 출력으로 한다 마르코프 체인은 행렬로 표현하고 연산하여 시스템의 신뢰도를 측정한다. 제안하는 시스템의 신뢰도 측정 방법은 부분이 가지고 있는 신뢰도가 전체 신뢰도에 미치는 영향을 산술적으로 측정할 수 있어 시스템이 요구하는 신뢰도에 접근할 수 있는 방법과 근거를 제공하는 장점이 있다.소시키는 장점을 갖는다.것으로 조사되었으며 40대 이상의 연령층은 점심비용으로 더 많은 지출을 하고 있는 것으로 나타났다. 4) 끼니별 한식에 대한 선호도는 아침식사의 경우가 가장 높았으며, 이는 40대와 50대에서 높게 나타났다. 점심 식사로 가장 선호되는 음식은 중식, 일식이었으며 저녁 식사에서 가장 선호되는 메뉴는 전 연령층에서 일식, 분식류 이었으며, 한식에 대한 선택 정도는 전 연령층에서 매우 낮게 나타났다. 5) 각 연령층에서 선호하는 한식에 대한 조사에서는 된장찌개가 전 연령층에서 가장 높은 선호도를 나타내었고, 김치는 40대 이상의 선호도가 30대보다 높게 나타났으며, 흥미롭게도 30세 이하의 선호도는 30대보다 높게 나타났다. 그 외에도 떡과 죽에 대한 선호도는 전 연령층에서 낮게 조사되었다. 장아찌류의 선호도는 전 연령대에서 낮았으며 특히 30세 이하에서 매우 낮게 조사되었다. 한식의 맛에 대한 만족도 조사에서는 연령이 올라갈수록 한식의 맛에 대한 만족도는 낮아지고 있었으나, 한식의 맛에 대한 만족도가 높을수록 양과 가격에 대한 만족도는 높은 경향을 나타내었다. 전반적으로 한식에 대한 선호도는 식사 때와 식사 목적에 따라 연령대 별로 다르게 나타나고 있으나, 선호도는 성별이나 세대에 관계없이 폭 넓은 선호도를 반영하고 있으며, 이는 대학생들을 대상으로 하는 연구 등에서도 나타난바 같다. 주 5일 근무제의 확산과 초 중 고생들의 토요일 휴무와 더불어 여행과 엔터테인먼트산업은 더욱 더 발전을 거듭하고 있으며, 외식은 여행과 여가 활동의 필수적인 요소로써 그 역할을 일조하고 있다. 이와 같은 여가시간의 증가는 독신자들에게는 좀더 많은 여유시간을 가족을 이루고 있는 가족구성원들에게는 가족과의 유대를 강화하는 휴식과 오락의 소비 트렌드를 창출시켰

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2006.05a
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• pp.1851-1856
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• 2006

영화는 대표적인 경험재로 가치판단이 주관적이고 제품 수명주기가 매우 짧아 예측의 불확실성이 높기 때문에 이를 정량적인 방법으로 모형화하기는 쉽지 않다. 이러한 한계점에도 불구하고 한 영화의 상업적 성공을 예측하는 것은 영화 제작자나 배급사, 극장 등 모든 주체에게 수익과 직결되는 중요한 문제이기 때문에 지금까지 다양한 통계 모형이 제시되었다. 그러나 이들 모형의 대부분은 영화흥행에는 영향을 미치나 측정할 수 없는 효과를 반영하지 못한다거나, 추정 모수의 효과가 모든 영화에 대해서 같다는 동일성 가정으로 인해 영화간 이질성을 고려하지 못하고 있다. 따라서, 본 연구에서는 추정 모수의 사전분포를 모호사전분포로 정의함으로써 변수들의 불확실성을 반영할 수 있고, 영화간 이질성을 고려할 수 있는 베이지안 선택 모형을 제안하였다. 모수의 사후분포는 마코프체인 몬테카를로 기법인 깁스 샘플러를 이용하여 추정하였다. 또한, 감독, 배우, 장르 등의 영화 별 속성 변수뿐만 아니라, 입소문에 의한 영화관람 결정 등의 구전효과와 경쟁영화의 개봉으로 인한 효과를 반영할 수 있는 변수를 추가하여 모형의 정확성을 높였다. 2005년과 2006년 상반기에 상영된 영화를 바탕으로 모형을 구축하고 인공신경망 모형과 비교한 결과, 전체적인 예측 정확도에서는 인공신경망 모형과 비슷한 결과를 보이나 상업적으로 성공한 영화를 예측하는 데에는 베이지안 선택모형이 보다 더 우수한 것으로 나타났다. 또한, 개봉 주의 경쟁심화 정도 및 개봉 첫 주의 스크린 수 등이 영화 흥행에 가장 중요한 변수로 나타났으며, 영화 개봉 전 그 영화에 대한 기대치가 높을수록 흥행 성적 또한 좋음을 알 수 있었다. 배우의 힘 및 계절성, 영화 평점 등은 이질성을 고려하지 않은 전체수준에서는 통계적으로 유의하지 않은 것으로 나타났으나, 그룹 간 이질성을 반영한 모형에서는 어느 정도 흥행한 영화를 만들기 위해서는 고려되어야 할 요소로 나타났다.렇지 않을 경우 적절한 벤치마킹 대상을 도출할 때까지 추가적인 분석과정을 반복한다. 제안한 방법을 통하여 조직은 기술적 생산 가능성 외에도 다양한 조직 운영 관점에서 적절한 벤치마킹 대상을 선정할 수 있으며, 이에 따른 목표를 수립할 수 있을 것으로 기대한다. 또한 더 나아가 global efficiency 관점에서 효율적 조직이 되기 위하여 단계적인 벤치마킹 대상 선정과 이에 따른 목표를 수립하는데도 유용하리라 판단된다.$1.20{\pm}0.37L$, 72시간에 $1.33{\pm}0.33L$로 유의한 차이를 보였으므로(F=6.153, P=0.004), 술 후 폐환기능 회복에 효과가 있다. 4) 실험군과 대조군의 수술 후 노력성 폐활량은 수술 후 72시간에서 실험군이 $1.90{\pm}0.61L$, 대조군이 $1.51{\pm}0.38L$로 유의한 차이를 보였다(t=2.620, P=0.013). 5) 실험군과 대조군의 수술 후 일초 노력성 호기량은 수술 후 24시간에서 $1.33{\pm}0.56L,\;1.00{\ge}0.28L$로 유의한 차이를 보였고(t=2.530, P=0.017), 술 후 72시간에서 $1.72{\pm}0.65L,\;1.33{\pm}0.3L$로 유의한 차이를 보였다(t=2.540, P=0.016). 6) 대상자의 술 후 폐환기능에 영향을 미치는 요인은 성별로 나타났다. 이에 따른 폐환기능의 차이를 보면, 실험군의 술 후 노력성 폐활량이 48시간에 남자($1.78{\pm}0.61L$)가 여자($1.27{\pm}0.45L$)보다 더 높게 나타났으며 (t=2.170, P=0.042), 72시간에도 역시 남자($2.16{\pm}0.56L$)가 여자($1.50{\pm}0.47L$)보다 더

• Asian-Australasian Journal of Animal Sciences
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• v.18 no.5
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• pp.613-619
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• 2005

Indigenous Yakutian cattle' adaptation to the hardest subarctic conditions makes them a valuable genetic resource for cattle breeding in the Siberian area. Since early last century, crossbreeding between native Yakutian cattle and imported Simmental and Kholmogory breeds has been widely adopted. In this study, variations at 22 polymorphic microsatellite loci in 5 populations of Yakutian, Kholmogory, Simmental, Yakutian-Kholmogory and Yakutian-Simmental cattle were analysed to estimate the genetic contribution of Yakutian cattle to the two hybrid populations. Three statistical approaches were used: the weighted least-squares (WLS) method which considers all allele frequencies; a recently developed implementation of a Markov chain Monte Carlo (MCMC) method called likelihood-based estimation of admixture (LEA); and a model-based Bayesian admixture analysis method (STRUCTURE). At population-level admixture analyses, the estimate based on the LEA was consistent with that obtained by the WLS method. Both methods showed that the genetic contribution of the indigenous Yakutian cattle in Yakutian-Kholmogory was small (9.6% by the LEA and 14.2% by the WLS method). In the Yakutian-Simmental population, the genetic contribution of the indigenous Yakutian cattle was considerably higher (62.8% by the LEA and 56.9% by the WLS method). Individual-level admixture analyses using STRUCTURE proved to be more informative than the multidimensional scaling analysis (MDSA) based on individual-based genetic distances. Of the 9 Yakutian-Simmental animals studied, 8 showed admixed origin, whereas of the 14 studied Yakutian-Kholmogory animals only 2 showed Yakutian ancestry (>5%). The mean posterior distributions of individual admixture coefficient (q) varied greatly among the samples in both hybrid populations. This study revealed a minor existing contribution of the Yakutian cattle in the Yakutian-Kholmogory hybrid population, but in the Yakutian-Simmental hybrid population, a major genetic contribution of the Yakutian cattle was seen. The results reflect the different crossbreeding patterns used in the development of the two hybrid populations. Additionally, molecular evidence for differences among individual admixture proportions was seen in both hybrid populations, resulting from the stochastic process in crossing over generations.

• Journal of Preventive Medicine and Public Health
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• v.24 no.4 s.36
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• pp.485-495
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• 1991

This study examined the effects of referral requirements for insurance patients which have been enforced since July 1, 1989 when medical insurance coverage was extended to the whole population except beneficiaries of medical assistance program. The requirements are mainly aimed at discouraging the use of tertiary care hospitals by imposing restrictions on the patient's choice of a medical service facility. The expectation is that such change in the pattern of medical care utilization would produce several desirable effects including increased efficiency in patient care and balanced development of various types of medical service facilities. In this study, these effects were assessed by the change in the number of out-patient visits and bed-days per illness episode and the share of each type of facility in the volume of services and the amount of expenditures after the implementation of the new referral system. The data for analysis were obtained from the claims to the insurance for government and school employees. The sample was drawn from the claims for the patients treated during the first six months of 1989, prior to the enforcement of referral requirements, and those of the patients treated during the first six months of 1990, after the enforcement. The 1989 sample included 299,824 claims (3.6% of total) and the 1990 sample included 332,131 (3.7% of total). The data were processed to make the unit of analysis an illness episode instead of an insurance claim. The facilities and types of care utilized for a given illness episode are defined to make up the pathway of medical care utilization. This pathway was conceived of as a Markov Chain process for further analysis. The conclusion emerged from the analysis is that the enforcement of referral requirements resulted in less use of tertiary care hospitals, and thereby decreased the volume of services and the amount of insurance expenses per illness episode. However, there are a few points that have to be taken into account in relation to the conclusion. The new referral system is likely to increase the use of medical services not covered by insurance, so that its impact on national health expenditures would be different from that on insurance expenditures. The extension of insurance coverage must have inereased patient load for all types of medical service organizations, and this increase may be partly responsible for producing the effects attributed to the new referral system. For example, excessive patient load for tertiary care hospitals may lead to the transfer of their patients to other types of facilities. Another point is that the data for this study correspond to very early phase of the new system. But both patients and medical care providers would adapt themselves to the new system to avoid or overcome its disadvantages for them, so as that its effects could change over time. Therefore, it is still necessary to closely monitor the impact of the referral requirements.

• The Korean Journal of Applied Statistics
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• v.33 no.1
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• pp.25-46
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• 2020

This paper presents ordinal probit semiparametric regression models using Bayesian Spectral Analysis Regression (BSAR) method. Ordinal probit regression is a way of modeling ordinal responses - usually more than two categories - by connecting the probability of falling into each category explained by a combination of available covariates using a probit (an inverse function of normal cumulative distribution function) link. The Bayesian probit model facilitates posterior sampling by bringing a latent variable following normal distribution, therefore, the responses are categorized by the cut-off points according to values of latent variables. In this paper, we extend the latent variable approach to a semiparametric model for the Bayesian ordinal probit regression with nonparametric functions using a spectral representation of Gaussian processes based BSAR method. The latent variable is decomposed into a parametric component and a nonparametric component with or without a shape constraint for modeling ordinal responses and predicting outcomes more flexibly. We illustrate the proposed methods with simulation studies in comparison with existing methods and real data analysis applied to a Korean National Health and Nutrition Examination Survey (KNHANES) 2016 for investigating nonparametric relationship between smoking behavior and coffee intake.

• Journal of the Korean Geographical Society
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• v.47 no.1
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• pp.98-120
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• 2012

The main objective of this study is to conduct subnational population projections of Korea based on a multiregional cohort-component method. This objective is accomplished by: (i) establishing a viable framework to implement the multiregional cohort-component method with reference to the Markov chain model and Rogers' multiregional population projection model; (ii) applying the established framework to subnational population projections of Korea, 2005~2030. The main results are twofold. First, the proposed method turns out to be highly valid in a methodological sense, which is seen from a high level of coincidence between the estimated and the observed. Second, the projection results turn out to be highly useful in the sense that interregional migration flow matrices are resulted for projection periods. The projected migration flows are expected to provide invaluable information for an understanding of future population change and for a formulation of policy alternatives. This study is strongly inspired by the multiregional perspective emphasizing the evolution of multiple regional populations interconnected by interregional migration flows rather than the overall national change.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.25 no.4
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• pp.355-362
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• 2012

Remaining useful life(RUL) prediction of a system is important in the prognostics field since it is directly linked with safety and maintenance scheduling. In the physics-based prognostics, accurately estimated model parameters can predict the remaining useful life exactly. It, however, is not a simple task to estimate the model parameters because most real system have multivariate model parameters, also they are correlated each other. This paper presents representative methods to estimate model parameters in the physics-based prognostics and discusses the difference between three methods; the particle filter method(PF), the overall Bayesian method(OBM), and the sequential Bayesian method(SBM). The three methods are based on the same theoretical background, the Bayesian estimation technique, but the methods are distinguished from each other in the sampling methods or uncertainty analysis process. Therefore, a simple physical model as an easy task and the Paris model for crack growth problem are used to discuss the difference between the three methods, and the performance of each method evaluated by using established prognostics metrics is compared.

• Molecules and Cells
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• v.28 no.5
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• pp.423-430
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• 2009

In order to elucidate the precise phylogenetic relationships of Korean wild boar (Sus scrofa coreanus), a partial mtDNA D-loop region (1,274 bp, NC_000845 nucleotide positions 16576-1236) was sequenced among 56 Korean wild boars. In total, 25 haplotypes were identified and classified into four distinct subgroups (K1 to K4) based on Bayesian phylogenetic analysis using Markov chain Monte Carlo methods. An extended analysis, adding 139 wild boars sampled worldwide, confirmed that Korean wild boars clearly belong to the Asian wild boar cluster. Unexpectedly, the Myanmarese/Thai wild boar population was detected on the same branch as Korean wild boar subgroups K3 and K4. A parsimonious median-joining network analysis including all Asian wild boar haplotypes again revealed four maternal lineages of Korean wild boars, which corresponded to the four Korean wild boar subgroups identified previously. In an additional analysis, we supplemented the Asian wild boar network with 34 Korean and Chinese domestic pig haplotypes. We found only one haplotype, C31, that was shared by Chinese wild, Chinese domestic and Korean domestic pigs. In contrast to our expectation that Korean wild boars contributed to the gene pool of Korean native pigs, these data clearly suggest that Korean native pigs would be introduced from China after domestication from Chinese wild boars.