• Title/Summary/Keyword: random censoring

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Determinants of High Risk Drinking in Korea (한국 사회의 고위험 음주 결정요인에 관한 연구: 중도 절단 이변량 프로빗 모형의 적용)

  • Chung Woojin
    • Korea journal of population studies
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    • v.26 no.2
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    • pp.91-110
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    • 2003
  • This study analyzed data from 1997 Korea's Behavioral Risk Factor Surveillance System Survey collected through telephone questionings based on the multi-stage stratified random sampling. We categorized respondents into those who had ever drunk an alcoholic beverage in the last month and those who didn't and, referring to the World Health Organization's guideline, the former group were further categorized into low risk drinking group and high risk drinking group. Employing bivariate probit regression analyses with censoring on independent variables such as preferred type of alcoholic beverage, the number of types of beverages consumed, age, marital status, education, occupation, residential area, current smoking, body mass index and stress suggested (1) that those who prefer soju are more likely to involve high risk drinking than those who and prefer the other alcoholic beverages (2) that those who are relatively older, who live without a partner, who have jobs, who. are vulnerable to stress, or who enjoy more than one type of beverage are more likely to be exposed to high risk drinking than the others.

Bayesian Estimations for the Two-parameter Exponential Model under the Type-II Censoring (제2종(第2種) 중단(中斷) 자료(資料)에서 두 모수지수분포(母數指數分布)의 베이지안 추정(推定))

  • Kim, Heon-Joo;Youn, Young-Hwa;Ko, Jeong-Hwan
    • Journal of the Korean Data and Information Science Society
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    • v.4
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    • pp.65-74
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    • 1993
  • Suppose that we have two populations(or systems), say ${\Pi}_{1}\;and\;{\Pi}_{2}$, to be tested. A random sample of size n from each population is taken and the test for each system will be terminated when the first r failures among n random samples are observed. This kind of test is caned the type-II censored (or item-censored) testing without replacement. Under this scheme we consider the problem of estimating the unknown parameters of interests and the reliability for a given time t for each population.

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An Estimation of Parameters in Weibull Distribution Using Least Squares Method under Random Censoring Model (임의 중단모형에서 최소제곱법을 이용한 와이블분포의 모수 추정)

  • Lee, Woo-Dong
    • 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.

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Accelerated Life Tests under Gamma Stress Distribution (스트레스함수가 감마분포인 가속수명시험)

  • 원영철
    • Journal of the Korea Safety Management & Science
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    • v.4 no.3
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    • pp.59-66
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    • 2002
  • This paper presents accelerated life tests for Type I censoring data under probabilistic stresses. Probabilistic stress, S, is the random variable for stress influenced by test environments, test equipments, sampling devices and use conditions. The hazard rate, $\theta$ is a random variable of environments and a function of probabilistic stress. In detail, it is assumed that the hazard rate is linear function of the stress, the general stress distribution is a gamma distribution and the life distribution for the given hazard rate, $\theta$is an exponential distribution. Maximum likelihood estimators of model parameters are obtained, and the mean life in use stress condition is estimated. A hypothetical example is given to show its applicability.

Nonparametric estimation of conditional quantile with censored data (조건부 분위수의 중도절단을 고려한 비모수적 추정)

  • Kim, Eun-Young;Choi, Hyemi
    • Journal of the Korean Data and Information Science Society
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    • v.24 no.2
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    • pp.211-222
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    • 2013
  • We consider the problem of nonparametrically estimating the conditional quantile function from censored data and propose new estimators here. They are based on local logistic regression technique of Lee et al. (2006) and "double-kernel" technique of Yu and Jones (1998) respectively, which are modified versions under random censoring. We compare those with two existing estimators based on a local linear fits using the check function approach. The comparison is done by a simulation study.

The Study for Software Future Forecasting Failure Time Using ARIMA AR(1) (ARIMA AR(1) 모형을 이용한 소프트웨어 미래 고장 시간 예측에 관한 연구)

  • Kim, Hee-Cheul;Shin, Hyun-Cheul
    • Convergence Security Journal
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    • v.8 no.2
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    • pp.35-40
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    • 2008
  • Software failure time presented in the literature exhibit either constant, monotonic increasing or monotonic decreasing. For data analysis of software reliability model, data scale tools of trend analysis are developed. The methods of trend analysis are arithmetic mean test and Laplace trend test. Trend analysis only offer information of outline content. In this paper, we discuss forecasting failure time case of failure time censoring. The used software failure time data for forecasting failure time is random number of Weibull distribution(shaper parameter 1, scale parameter 0.5), Using this data, we are proposed to ARIMA(AR(1)) and simulation method for forecasting failure time. The practical ARIMA method is presented.

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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.

Analysis of Tumorigenicity Data with Informative Censoring (종속적인 중도절단을 가진 동물종양 자료의 분석을 위한 모형)

  • Kim, Jin-Heum;Kim, Youn-Nam
    • The Korean Journal of Applied Statistics
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    • v.23 no.5
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    • pp.871-882
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    • 2010
  • In animal tumorigenicity data, the occurrence time of tumor is not observed because the existence of a tumor is examined only at either time of natural death or time of sacrifice for the animal. A three-state model (Health-Tumor onset-Death) is widely used to model the incomplete data. In this paper, we employed a frailty effect into the three-state model to incorporate the dependency of death on tumor occurrence when the time of natural death works as an informative censoring against the tumor onset time. For the inference of parameters, then the EM algorithm is considered in order to deal with missing quantities of tumor onset time and random frailty. The proposed method is applied to the bladder tumor data taken from Lindsey and Ryan (1993, 1994) and a simulation study is performed to show the behavior of the proposed estimators.

Estimation of Conditional Kendall's Tau for Bivariate Interval Censored Data

  • Kim, Yang-Jin
    • Communications for Statistical Applications and Methods
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    • v.22 no.6
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    • pp.599-604
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    • 2015
  • Kendall's tau statistic has been applied to test an association of bivariate random variables. However, incomplete bivariate data with a truncation and a censoring results in incomparable or unorderable pairs. With such a partial information, Tsai (1990) suggested a conditional tau statistic and a test procedure for a quasi independence that was extended to more diverse cases such as double truncation and a semi-competing risk data. In this paper, we also employed a conditional tau statistic to estimate an association of bivariate interval censored data. The suggested method shows a better result in simulation studies than Betensky and Finkelstein's multiple imputation method except a case in cases with strong associations. The association of incubation time and infection time from an AIDS cohort study is estimated as a real data example.

Conditional Bootstrap Methods for Censored Survival Data

  • Kim, Ji-Hyun
    • Journal of the Korean Statistical Society
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    • v.24 no.1
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    • pp.197-218
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    • 1995
  • We first consider the random censorship model of survival analysis. Efron (1981) introduced two equivalent bootstrap methods for censored data. We propose a new bootstrap scheme, called Method 3, that acts conditionally on the censoring pattern when making inference about aspects of the unknown life-time distribution F. This article contains (a) a motivation for this refined bootstrap scheme ; (b) a proof that the bootstrapped Kaplan-Meier estimatro fo F formed by Method 3 has the same limiting distribution as the one by Efron's approach ; (c) description of and report on simulation studies assessing the small-sample performance of the Method 3 ; (d) an illustration on some Danish data. We also consider the model in which the survival times are censered by death times due to other caused and also by known fixed constants, and propose an appropriate bootstrap method for that model. This bootstrap method is a readily modified version of the Method 3.

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