• Title, Summary, Keyword: 중도절단 자료

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Estimation of Survival Function and Median Survival Time in Interval-Censored Data (구간중도절단자료에서 생존함수와 중간생존시간에 대한 추정)

  • Yun, Eun-Young;Kim, Choong-Rak
    • The Korean Journal of Applied Statistics
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    • v.23 no.3
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    • pp.521-531
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    • 2010
  • Interval-censored observations are common in medical and epidemiologic studies; however, limited studies exist due to the complexity and special structure of interval-censoring. This paper introduces the imputation method and the self consistency method in the interval-censored data. We propose a new method of generating random numbers under an interval-censoring set-up. Through simulation studies we compare two methods under various simulation schemes in the sense of the mean squared error for estimating the median survival time and the mean integrated squared error for estimating the survival function. Under a moderate censoring percentage, the mean imputation method showed a better performance than the self-consistency method in estimating the median survival time and the survival function.

Goodness of Fit Tests for the Exponential Distribution based on Multiply Progressive Censored Data (다중 점진적 중도절단에서 지수분포의 적합도 검정)

  • Yun, Hyejeong;Lee, Kyeongjun
    • Journal of the Korean Data Analysis Society
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    • v.20 no.6
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    • pp.2813-2827
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    • 2018
  • Progressive censoring schemes have become quite popular in reliability study. Under progressive censored data, however, some units can be failed between two points of observation with exact times of failure of these units unobserved. For example, loss may arise in life-testing experiments when the failure times of some units were not observed due to mechanical or experimental difficulties. Therefore, multiply progressive censoring scheme was introduced. So, we derives a maximum likelihood estimator of the parameter of exponential distribution. And we introduced the goodness-of-fit test statistics using order statistic and Lorenz curve. We carried out Monte Carlo simulation to compare the proposed test statistics. In addition, real data set have been analysed. In Weibull and chi-squared distributions, the test statistics using Lorenz curve are more powerful than test statistics using order statistics.

중도절단된 생존함수의 신뢰구간 비교연구

  • Lee, Gyeong-Hwa;Lee, Jae-Won
    • Proceedings of the Korean Statistical Society Conference
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    • pp.251-255
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    • 2005
  • 중도절단된 자료와 표본수가 적은 자료를 가지는 생존분석에서 생존율을 추정하거나 두 집단의 생존율을 비교할 때 정규분포 근사를 가정한 신뢰구간을 이용하는 데는 많은 어려움이 생긴다. 생존함수의 신뢰구간에 대한 중도절단을, 표본의 크기에 따른 다양한 상황의 모의실험을 통하여 Kaplan-Meier, Nelson, 적률 추정량 그리고 cox model의 ${\beta}$을 가지고 붓스트랩을 이용한 신뢰구간과 비모수 신뢰구간, 우도비 신뢰구간의 실제 포함 확률을 비교해보고자 한다.

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Analysis of Interval-censored Survival Data from Crossover Trials with Proportional Hazards Model (교차계획 구간절단 생존자료의 비례위험모형을 이용한 분석)

  • Kim, Eun-Young;Song, Hae-Hiang
    • The Korean Journal of Applied Statistics
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    • v.20 no.1
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    • pp.39-52
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    • 2007
  • Crossover trials of new drugs in the treatment of angina pectoris, which frequently use treadmill exercise test for the assessment of its efficacy, produce censored survival times. In this paper we consider analysis approaches for censored survival times from crossover trials. Previously, a stratified Cox model for paired observation and nonparametric methods have been presented as possible analysis methods. On the other hand, the differences of two survival times would produce interval-censored survival times and we propose a Cox model for interval-censored data as n alternative analysis method. Example data is analyzed in order to compare these different methods.

A Modification of the Shapiro-Wilk Test for Exponentiality Based on Censored Data (중도절단자료에 대한 수정된 SHAPIRO-WILK 지수 검정)

  • Kim, Nam-Hyun
    • The Korean Journal of Applied Statistics
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    • v.21 no.2
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    • pp.265-273
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    • 2008
  • Kim (2001a) presented a modification of the Shapiro and Wilk (1972) test for exponentiality based on the ratio of two asymptotically efficient estimates of scale. In this paper we modify this test statistic when the sample is censored. We use the normalized spacings based on the sample data, which was used in Samanta and Schwarz (1988) to modify the Shapiro and Wilk (1972) statistic to the censored data. As a result the modified statistics have the same null distribution as the uncensored case with a corresponding reduction in sample size. Through a simulation study it is found that the proposed statistic has higher power than Samanta and Schwarz (1988) statistic especially for the alternatives with the coefficient of variation greater than or equal to 1.

Generating censored data from Cox proportional hazards models (Cox 비례위험모형을 따르는 중도절단자료 생성)

  • Kim, Ji-Hyun;Kim, Bongseong
    • The Korean Journal of Applied Statistics
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    • v.31 no.6
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    • pp.761-769
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    • 2018
  • Simulations are important for survival analyses that deal with censored data. Cox models are widely used in survival analyses, therefore, we investigate how to generate censored data that can simulate the Cox model. Bender et al. (Statistics in Medicine, 24, 1713-1723, 2005) provided a parametric method for generating survival times, but we need to generate censoring times as well as survival times to simulate the censored data. In addition to the parametric method for generating censored data, a nonparametric method is also proposed and applied to a real data set.

A binomial CUSUM chart for monitoring type I right-censored Weibull lifetimes (제1형의 우측중도절단된 와이블 수명자료를 관리하는 이항 누적합 관리도)

  • Choi, Min-jae;Lee, Jaeheon
    • The Korean Journal of Applied Statistics
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    • v.29 no.5
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    • pp.823-833
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    • 2016
  • The lifetime is a key characteristic of product quality. It is best to obtain the lifetime data of all samples, but they are often censored due to time or expense limitations. In this paper, we propose a binomial cumulative sum (CUSUM) chart to monitor the mean of type I right-censored Weibull lifetime data, for a xed value of the Weibull shape parameter. We compare the performance of the proposed binomial CUSUM chart with CUSUM charts studied previously using the steady-state average run length (ARL). The results show that the performance of the binomial CUSUM chart is better when the censoring rate is high and/or the sample size is small.

Optimal Sampling Method of Censored Data for Optimizing Preventive Maintenance (예방정비 최적화를 위한 중도절단 자료의 최적 샘플링 방안)

  • Lee, In-Hyun;Oh, Sea-Hwa;Li, Chang-Long;Yang, Dong-In;Lee, Key-Seo
    • Journal of the Korean Society for Railway
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    • v.16 no.3
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    • pp.196-201
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    • 2013
  • As there is no failure data for the entire lifecycle of a product, when analyzing reliability measures based on early failure data only, there may be a significant error between the estimated mean life and the real one, because it can be underestimated, or on the other hand, it can be overestimated when analyzing reliability measures based on a large amount of censored data with the failure data. To resolve the issue, this study proposes an optimal sampling estimation procedure that selects the proportion of censored data to estimate the optimal distribution with the idea that the estimated distribution could be approximated as closely as the real life distribution. This would work if we sampled the optimal proportion on the censored data, because failure data has real intrinsic distribution in any situation. We validate the proposed procedure using an actual example. If the proposed method is applied to the maintenance policy of TWC (Train to Wayside Communication) system, then we can establish the optimal maintenance policy. Thus, we expect that it will be effective for improvement of reliability and cost savings.

A concordance test for bivariate interval censored data using a leverage bootstrap (지렛대 붓스트랩을 이용한 이변량 구간 중도 절단 자료의 일치성 검정)

  • Kim, Yang-Jin
    • The Korean Journal of Applied Statistics
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    • v.32 no.5
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    • pp.753-761
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    • 2019
  • A test procedure based on a Kendall's τ statistic is proposed for the association of bivariate interval censored data. In particular, a leverage bootstrap technique is applied to replace unknown failure times and a classical adjustment method is applied for treating tied observations. The suggested method shows desirable results in simulation studies. An AIDS dataset is analyzed with the suggested method.

Testing Log Normality for Randomly Censored Data (임의중도절단자료에 대한 로그정규성 검정)

  • Kim, Nam-Hyun
    • The Korean Journal of Applied Statistics
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    • v.24 no.5
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    • pp.883-891
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    • 2011
  • For survival data we sometimes want to test a log normality hypothesis that can be changed into normality by transforming the survival data. Hence the Shapiro-Wilk type statistic for normality is generalized to randomly censored data based on the Kaplan-Meier product limit estimate of the distribution function. Koziol and Green (1976) derived Cram$\acute{e}$r-von Mises statistic's randomly censored version under the simpl hypothesis. These two test statistics are compared through a simulation study. As for the distribution of censoring variables, we consider Koziol and Green (1976)'s model and other similar models. Through the simulation results, we can see that the power of the proposed statistic is higher than that of Koziol-Green statistic and that the proportion of the censored observations (rather than the distribution of censoring variables) has a strong influence on the power of the proposed statistic.