• The Korean Journal of Applied Statistics
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• v.20 no.2
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• pp.313-322
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• 2007

Several robust censored depth regression methods are compared under contamination. Park and Hwang(2003) suggested a way to circumvent the censoring issue by incorporating Kaplan-Meier type weight in halfspace regression depth and Park(2003) used a similar technique to simplicial regression depth. Hubert et al. (2001) suggested a high breakdown point regression depth based on projection called rcent. A new method to implement censoring in rcent is suggested and compared with two precedents under various contamination and censoring schemes.

• Journal of the Korean Data and Information Science Society
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• v.9 no.1
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• pp.37-45
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• 1998

We consider the problem of obtaining the confidence bands for the survival function with incomplete data. It is a rather simple procedure for constructing confidence bands of survival function. This method uses the weak convergence of normalized cumulative hazard estimator to a mean zero Gaussian process whose distribution can be easily approximated through simulation. Finally, we compare the performance of the proposed confidence bands through Monte Carlo simulation and we applied to construct the proposed bands with the Leukemia patient data.

• The Korean Journal of Applied Statistics
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• v.22 no.1
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• pp.141-151
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• 2009

According to the type of microdata, the various methods have been in use for masking microdata. Multiplicative noise is the one of popular schemes for masking continuous variables. In this paper, we introduce the method of masking based on multiplicative noise and show some results of the application on the 2006 Householder Income and Expenditure Survey (HIES) data. To create the multiplicative noise factor, we used the triangular distribution. truncated triangular distribution, trapezoidal distribution, and double triangular distribution. Also, formulas for the domain estimation for the data masked by the multiplicative noise are developed.

• The Korean Journal of Applied Statistics
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• v.22 no.3
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• pp.595-606
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• 2009

Two tests were introduced for comparing several survival functions with doubly interval-censored data and illustrated with data surveyed by Korean Cancer Prevention Study (Jee et al., 2005). The test which extended Kim et al. (2006)'s test to the doubly interval-censored data has an advantage over Sun (2006)'s test in terms of saving computation time because the proposed test only depends on the size of risk set, and also the proposed test is applicable to continuous failure time data as well as discrete failure time data unlike Sun's test. Comparing male with female groups on the incubation time of diabetes was highly different and the survival of female group was longer than that of male one. Regardless of gender, the difference in survival functions of four age groups was highly significant with p-value of less than 0.001. This trend was more remarkable for female group than for male one. Simulation results showed that the significance level of both tests was well controlled and the proposed test was better than Sun's test in terms of power.

• Ecology and Resilient Infrastructure
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• v.8 no.4
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• pp.194-203
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• 2021

With the recent increase in maintenance works on water and sewer pipes as well as district heating supply pipes, pavement cutting work using pavement cutter is on the rise. The pavement cutting operation generates considerable dust (cutting sludge) as well as noise; therefore, it is necessary to apply eco-friendly technologies that have low noise and dust recovery capability. Thus far, various equipment for recovering dust have been developed; however, there is a limitation in that the environmental friendliness is not quantified. Therefore, in this study, we developed a low-noise, dust-recovery type pavement cutter that can fundamentally remove the causes of environmental hazards such as noise and dust and evaluated the eco-friendliness of the pavement cutting process performed by this cutter. To this end, an integrated water cooling-sludge recovery system composed of a vacuum device and a sludge suction unit was developed, and the developed system was applied to a pavement cutter. Subsequently, the developed equipment was applied to the test bed, and data related to its eco-friendliness were collected and evaluated. The results showed that the cutting sludge recovery rate of the developed equipment was greater than 83%, the noise level was approximately 82 - 83 dB, and the sound power level was 115 dB. The results of this study will be used as basic data to develop improved pavement cutters in the future with improved cutting sludge recovery performance and lower noise.

• The Korean Journal of Applied Statistics
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• v.29 no.7
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• pp.1311-1327
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• 2016

We propose a multi-state model for analyzing semi-competing risks data with interval-censored or missing intermediate events. This model is an extension of the 'illness-death model', which composes three states, such as 'healthy', 'diseased', and 'dead'. The state of 'diseased' can be considered as an intermediate event. Two more states are added into the illness-death model to describe missing events caused by a loss of follow-up before the end of the study. One of them is a state of 'LTF', representing a lost-to-follow-up, and the other is an unobservable state that represents the intermediate event experienced after LTF occurred. Given covariates, we employ the Cox proportional hazards model with a normal frailty and construct a full likelihood to estimate transition intensities between states in the multi-state model. Marginalization of the full likelihood is completed using the adaptive Gaussian quadrature, and the optimal solution of the regression parameters is achieved through the iterative Newton-Raphson algorithm. Simulation studies are carried out to investigate the finite-sample performance of the proposed estimation procedure in terms of the empirical coverage probability of the true regression parameter. Our proposed method is also illustrated with the dataset adapted from Helmer et al. (2001).

• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.281-285
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• 2011

본 연구에서는 연최대치 독립 호우사상 계열과 연최대치 계열의 차이를 살펴보았다. 이를 위해 본 연구에서는 몇 가지 경우의 IETD 및 절단값을 적용하여 독립 호우사상을 결정하고, 그 특성을 살펴보았다. 이어 연최대치 계열과 연 최대치 독립 호우사상 계열을 비교하였다. 본 연구는 1961년부터 2010년까지 서울지점의 시강우 자료를 분석대상으로 사용하였다. 그 결과, IETD의 증가에 따라서 독립 호우사상의 발생빈도 및 평균 강우강도는 감소하고, 평균 지속기간은 증가하였다. 절단값의 증가에 따라 독립 호우사상의 발생빈도 및 평균 지속기간은 감소하고, 평균 강우강도는 증가하였다. 호우사상의 평균 강우강도는 강우 지속기간에 관계없이 거의 일정한 것으로 나타났다. 이러한 결과를 통해 지속기간이 짧은 호우사상의 최대 강우강도는 지속기간이 긴 호우사상의 최대 강우강도보다 매우 작을 것으로 파악되었다. 지속 기간이 짧은 경우, 연 최대치 계열과 연 최대치 독립 호우사상 계열의 차이는 매우 크며, 강우 지속기간이 길게 적용한 경우에는, 두 계열의 차이는 매우 줄어드는 것으로 나타났다.

• Communications for Statistical Applications and Methods
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• v.17 no.6
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• pp.811-827
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• 2010

This paper deals with a density estimation method in binary choice models that can be regarded as a statistical inverse problem. We use an orthogonal basis to estimate density function and consider the choice of an appropriate truncation parameter to reflect the model complexity and the prediction accuracy. We propose a data-dependent rule to choose the truncation parameter in the context of binary choice models. A numerical simulation is provided to illustrate the performance of the proposed method.

• The Korean Journal of Applied Statistics
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• v.11 no.1
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• pp.113-127
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• 1998

There have been a great deal of interests in comparing two survival distributins in clinical trials. This paper compares some well-known statistical methods for testing the equality of two survival distributions. Simulation studies also provide some insights into the properties of these test statistics across several types of survival distributions and degrees of censorship.

• The Korean Journal of Applied Statistics
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• v.28 no.3
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• pp.467-475
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• 2015

Accurate demand forecasting is a crucial component in revenue management(RM). The booking data of departed flights is used to forecast the demand for future departing flights; however, some booking requests that were denied were omitted in the departed flights data. Denied booking requests can be interpreted as censored in statistics. Thus, unconstraining demand is an important issue to forecast the true demands of future flights. Several unconstraining methods have been introduced and a method based on expectation maximization is considered superior. In this study, we propose a new unconstraining method based on a regression model that can entertain such censored data. Through a simulation study, the performance of the proposed method was evaluated with two representative unconstraining methods widely used in RM.