• The Korean Journal of Applied Statistics
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• v.16 no.2
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• pp.273-282
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• 2003

The problem of estimating the parameters of k-population Weibull distributions is discussed under the prior of ordered scale parameters. Parameters are estimated by the Gibbs sampling method. Since the conditional posterior distribution of the shape parameter in the Gibbs sampler is not log-concave, the shape parameter is generated by the adaptive rejection sampling. Finally, we applied this estimation methodology to the data discussed in Nelson (1970).

• Journal of the Korean Data and Information Science Society
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• v.7 no.2
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• pp.263-272
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• 1996

In this parer, under random censorship model, an estimation of scale and shape parameters in Weibull lifetime model is considered. Based on nonparametric estimator of survival function, the least square method is proposed. The proposed estimation method is simple and the performance of the proposed estimator is as efficient as maximum likelihood estimators. An example is presented, using field winding data. Simulation studies are performed to compare the performaces of the proposed estimator and maximum likelihood estimator.

• The Korean Journal of Applied Statistics
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• v.11 no.2
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• pp.351-362
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• 1998

In this paper, a test of fit for Weibull distribution on the estimated Kullback-Leibler information is proposed. The test uses the Vasicek entropy estimates, so to compute it a window size m must first be fried, and then is obtained critical values computed by Monte Carlo simulations. The power of the proposed test under various alternatives is compares with that of ocher famous tests. The use of the test is shown in an illustrative example.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.23 no.58
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• pp.81-87
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• 2000

대수정규분포와 와이블분포는 비정규분포를 하는 공정특성에 반영된다. Hahn 과 Shapir(1967)의 수치 예를 통해 이러한 대수정규분포와 와이블분포를 식별하는 검정방법으로 최우비 검정(RML)을 사용하였다. 검정결과 와이블분포를 하는 공정으로 판단되어, 와이블분포 의 모수 추정은 실무에서 그래프와 수식으로도 쉽게 추정할 수 있는 수정적률추정량(MME)를 이용하여 공정 능력을 평가하였다. 공정능력의 평가 측도로 공정능력지수와 불량률(PPM)의 측도와 병행하여 나타내었다. 공정능력 평가의 결과로 와이블분포를 하는 공정을 대수정규분포로 잘못 판단함으로써 발생하는 오류를 2가지 측도로 표현함으로써 올바르게 공정능력을 판단할 수 있도록 종합적인 정보를 제시하였다.

• The Korean Journal of Applied Statistics
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• v.20 no.2
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• pp.357-371
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• 2007

For the time-to-failure data with competing risks, cumulative incidence functions (CIFs) are commonly estimated using nonparametric methods. If the cases of events due to the cause of primary interest are infrequent relative to other cause of failure, nonparametric methods may result in rather imprecise estimates for CIF. In such cases, Bryant et al. (2004) suggested to model the cause-specific hazard of primary interest parametrically, while accounting for the other modes of failure using nonparametric estimator. We represented the semiparametric cumulative incidence estimator and extended to the model of Weibull and log-normal distribution. We also conducted simulations to access the performance of the semiparametric cumulative incidence estimators and to investigate the impact of model misspecification in log-normal cause-specific hazard model.

• Journal of the Korean Data and Information Science Society
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• v.11 no.2
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• pp.295-302
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• 2000

We study the efficient method to estimate the parameters for the Weibull model with covariates which occupies an important position in survival analysis. A treatment period may be divided by the stages of treatments under the different treatment arams. The piecewise method is considered to obtain the estimators of the parameters by maximum likelihood method. We explore the real data to show that the piecewise is more efficient than the nonpiecewise to estimate the parameters.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.11a
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• pp.339-343
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• 2009

The aim of the study was to investigate the statistical distribution of muzzle velocity of 155mm propelling charge K676 which is for the use of K9, a korean 155mm self-propelled artillery. A plenty of muzzle velocity data were collected from lot assessment test of propelling charge. The muzzle velocity of each test round is compensated by reference round. In the present work, the detailed statistical analysis of the muzzle velocity data is carried out using probability models including normal, Weibull 2-parameter and Weibull 3-parameter distributions. The results of goodness of fit test showed that the normal distribution described more appropriately the experimentally measured muzzle velocity data and the Weibull distribution is also applicable. The coefficient of variation showed that the mass production capability of each propelling charge lot has been maintained.

• Proceedings of the KSME Conference
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• 2001.11a
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• pp.272-277
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• 2001

In order to evaluate variation of fatigue data of the LP steam turbine blade steel, it is important to estimate P - S - N curves to accurately define the probability distributions. In this study, new procedure is introduced to determine the expression of P - S - N curves. For this purpose, 3-parameter Weibull distribution was found to be most appropriate among assumed distributions when the probability distributions of the fatigue life were examined by the proposed analysis. Furthermore, parameter estimation for P - S - N curves was performed using various optimization to maximize the correlation coefficient. As a result of this, sequential linear programing method is used for estimation of P - S - N curves.

• Journal of the Korean Data and Information Science Society
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• v.20 no.3
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• pp.485-492
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• 2009

In this paper, we studied process capability analysis for brake-pad manufacturing system and considered Weibull, normal and logistic distributions for density estimation of wear life of brake pads for a passenger car with a real data. These three distributions are seem to work well. Estimated percentiles of brake pads can be used to evaluate the design criteria and customers' need for brake pads.

• The Korean Journal of Applied Statistics
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• v.12 no.2
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• pp.463-478
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• 1999

가속수명시험은 제품의 사용조건 보다 높은 스트레스 수준에서 시험하여 제품의 신뢰수명을 추정하는 것으로써 스트레스 수준을 일정하게 유지하는 일정형 시험이 일반적이다. 그러나 경우에 따라서는 시험절차의 편리와 시험기간의 단축을 위해서 스트레스를 시간에 따라 선형적으로 증가시키는 램프(ramp)형 시험을 사용하기도 한다. 이 논문에서는 일정스트레 s에서 제품의 수명이 모수 $\Theta$(s), $\beta$인 와이블분포를 따르고 수명과 스트레스의 관계가 역거듭제곱모형인 경우에 스트레스를 사용조건에서 가하고, 스트레스 수준의 최대 한계가 주어져 있는 램프시험 하에서 시험제품이 갖는 수명분포를 유도하고, 정시관측중단시험의 경우에 대해서 수명분포의 최우추정량과 추정량의 점근분포를 구하며, 최우추정치를 구하는 알고리즘을 제안한다.