• Title/Summary/Keyword: Time censoring

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Bayes estimation of entropy of exponential distribution based on multiply Type II censored competing risks data

  • Lee, Kyeongjun;Cho, Youngseuk
    • Journal of the Korean Data and Information Science Society
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    • v.26 no.6
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    • pp.1573-1582
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    • 2015
  • In lifetime data analysis, it is generally known that the lifetimes of test items may not be recorded exactly. There are also situations wherein the withdrawal of items prior to failure is prearranged in order to decrease the time or cost associated with experience. Moreover, it is generally known that more than one cause or risk factor may be present at the same time. Therefore, analysis of censored competing risks data are needed. In this article, we derive the Bayes estimators for the entropy function under the exponential distribution with an unknown scale parameter based on multiply Type II censored competing risks data. The Bayes estimators of entropy function for the exponential distribution with multiply Type II censored competing risks data under the squared error loss function (SELF), precautionary loss function (PLF) and DeGroot loss function (DLF) are provided. Lindley's approximate method is used to compute these estimators.We compare the proposed Bayes estimators in the sense of the mean squared error (MSE) for various multiply Type II censored competing risks data. Finally, a real data set has been analyzed for illustrative purposes.

A Study on the Survival Probability and Survival Factors of Small and Medium-sized Enterprises Using Technology Rating Data (기술평가 자료를 이용한 중소기업의 생존율 추정 및 생존요인 분석)

  • Lee, Young-Chan
    • Knowledge Management Research
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    • v.11 no.2
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    • pp.95-109
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    • 2010
  • The objectives of this study are to identify the survival function (hazard function) of small and medium enterprises by using technology rating data for the companies guaranteed by Korea Technology Finance Corporation (KOTEC), and to figure out the factors that affects their survival. To serve the purposes, this study uses Kaplan-Meier Analysis as a non-parametric method and Cox proportional hazards model as a semi-parametric one. The 17,396 guaranteed companies that assessed from July 1st in 2005 to December 31st in 2009 are selected as samples (16,504 censored data and 829 accident data). The survival time is computed with random censoring (Type III) from July in 2005 as a starting point. The results of the analysis show that Kaplan-Meier Analysis and Cox proportional hazards model are able to readily estimate survival and hazard function and to perform comparative study among group variables such as industry and technology rating level. In particular, Cox proportional hazards model is recognized that it is useful to understand which technology rating items are meaningful to company's survival and how much they affect it. It is considered that these results will provide valuable knowledge for practitioners to find and manage the significant items for survival of the guaranteed companies through future technology rating.

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Study on the Reliability Evaluation Method of Components when Operating in Different Environments (이종 환경에서 운용되는 부품의 신뢰도 평가 방법 연구)

  • Hwang, Jeong Taek;Kim, Jong Hak;Jeon, Ju Yeon;Han, Jae Hyeon
    • Journal of the Korean Society of Safety
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    • v.32 no.5
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    • pp.115-121
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    • 2017
  • This paper is to introduce the main modeling assumptions and data structures associated with right-censored data to describe the successful methodological ideas for analyzing such a field-failure-data when components operating in different environments. The Kaplan - Meier method is the most popular method used for survival analysis. Together with the log-rank test, it may provide us with an opportunity to estimate survival probabilities and to compare survival between groups. An important advantage of the Kaplan - Meier curve is that the method can take into account some types of censored data, particularly right-censoring. The above non-parametric method was used to verify the equality of parts life used in different environments. After that, we performed the life distribution analysis using the parametric method. We simulated data from three distributions: exponential, normal, and Weibull. This allowed us to compare the results of the estimates to the known true values and to quantify the reliability indices. Here we used the Akaike information criterion to find a suitable life time distribution. If the Akaike information criterion is the smallest, the best model of failure data is presented. In this paper, no-nparametrics and parametrics methods are analyzed using R program which is a popular statistical program.

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.

Optimum failure-censored step-stress partially accelerated life test for the truncated logistic life distribution

  • Srivastava, P.W.;Mittal, N.
    • International Journal of Reliability and Applications
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    • v.13 no.1
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    • pp.19-35
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    • 2012
  • This paper presents an optimum design of step-stress partially accelerated life test (PALT) plan which allows the test condition to be changed from use to accelerated condition on the occurrence of fixed number of failures. Various life distribution models such as exponential, Weibull, log-logistic, Burr type-Xii, etc have been used in the literature to analyze the PALT data. The need of different life distribution models is necessitated as in the presence of a limited source of data as typically occurs with modern devices having high reliability, the use of correct life distribution model helps in preventing the choice of unnecessary and expensive planned replacements. Truncated distributions arise when sample selection is not possible in some sub-region of sample space. In this paper it is assumed that the lifetimes of the items follow Truncated Logistic distribution truncated at point zero since time to failure of an item cannot be negative. Optimum step-stress PALT plan that finds the optimal proportion of units failed at normal use condition is determined by using the D-optimality criterion. The method developed has been explained using a numerical example. Sensitivity analysis and comparative study have also been carried out.

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Survival Rate of Intrahepatic Cholangiocarcinoma Patients after Surgical Treatment in Thailand

  • Sriputtha, Sudarat;Khuntikeo, Narong;Promthet, Supannee;Kamsaard, Supot
    • Asian Pacific Journal of Cancer Prevention
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    • v.14 no.2
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    • pp.1107-1110
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    • 2013
  • Intrahepatic cholangiocarcinoma (ICC), one of the primary liver cancers, is frequent in the northeastern part of Thailand. Surgical resection remains the best method of treatment, but patients suffering from ICC usually present at a late stage of the disease. Studies of survival and prognostic factors after surgery remain rare. The aim here was to evaluate the survival rate and factors affecting the survival of patients with intrahepatic cholangiocarcinoma after surgery. The study used a retrospective cohort design. The subjects were 73 consecutive patients with ICC, who were admitted for surgery to Srinagarind Hospital, Khon Kaen University, during the period 2005-2009. The censoring date was 31 December, 2011, data being evaluated using uni- and multivariate analyses. Postoperative survival analysis was performed by the Kaplan-Meier method, and the Cox proportional hazard model was used to identify independent prognostic factors. The total follow-up time was 99 person-years. The total number of deaths was 59, giving a mortality rate of 59 per 100 person-years. The cumulative 1-, 3-, and 5-year survival rates were 52.1%, 21.7%, and 11.2%, respectively. The median duration of survival after resection was 12.4 months. Univariate analysis revealed stage of disease, lymph node metastasis, histological type, histological grade and macroscopic classification to be statistically significant (p-value<0.05) prognostic factors. In the multivariate analysis, only macroscopic classification was statistically significant (p-value<0.05). In conclusion, macroscopic classification was the only independent factor found to be significantly associated with survival following surgical treatment of ICC.

Estimation of the survival function of the legislative process in Korea: based on the experiences of the 17th, 18th, and 19th National Assembly of Korea (국회 법안 검토 기간의 생존함수 추정: 제 17, 18, 19대 국회의 사례를 바탕으로)

  • Yun, Yeonggyu;Cho, Yunsoo;Jung, Hye-Young
    • The Korean Journal of Applied Statistics
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    • v.32 no.4
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    • pp.503-515
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    • 2019
  • In this study we estimate the survival function of duration of the legislative processes in the 17th, 18th, and 19th National Assembly of Korea, and further analyze effects of the political situation variables on the legislative process. We define the termination of legislative process from a novel perspective to alleviate issues of dependency between censoring and failure in the data. We also show that the proportional hazards assumption does not hold for the data, and analyze data employing a log-normal accelerated failure time model. The policy areas of law agendas are shown to affect the speed of legislative process in different ways and legislative process tends to be prompt in times of divided governments.

Survival analysis of spinal muscular atrophy type I

  • Park, Hyun-Bin;Lee, Soon-Min;Lee, Jin-Sung;Park, Min-Soo;Park, Kook-In;NamGung, Ran;Lee, Chul
    • Clinical and Experimental Pediatrics
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    • v.53 no.11
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    • pp.965-970
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    • 2010
  • Purpose: The life expectancy of patients with spinal muscular atrophy (SMA) type I is generally considered to be less than 2 years. Recently, with the introduction of proactive treatments, a longer survival and an improved survival rate have been reported. In this study, we analyzed the natural courses and survival statistics of SMA type I patients and compared the clinical characteristics of the patients based on their survival periods. Methods: We reviewed the medical records of 14 pediatric patients diagnosed with SMA type I during a 9-year period. We examined the demographic and clinical characteristics of these patients, calculated their survival probabilities, and plotted survival curves as on the censoring date, January 1, 2010. We also compared the characteristics of the patients who died before the age of 24 months (early-death, ED group) and those who survived for 24 months or longer (long-survival, LS group). Results: The mean survival time was $22.8{\pm}2.0$ months. The survival probabilities at 6 months, 12 months, 18 months, 24 months, and 30 months were 92.9%, 92.9%, 76.0%, 76.0%, and 65.1%, respectively. Birth weight was the only factor that showed a statistically significant difference between the ED and LS groups ($P$=0.048). Conclusion: In this study, the survival probabilities at 2 years were far greater than expected. Because of the limited number of patients and information in this study, the contribution of improved supportive care on longer survival could not be clarified; this may be elucidated in larger cohort studies.

Comparison of Cancer Survival by Age Group for 1997 and for 2002: Application of Period Analysis using the National Cancer Incidence Database (국가 암 발생 데이터베이스에 등록된 암환자의 연령군별 생존율: 기간 분석 방식에 의한 1997년과 2002년도 생존율 비교)

  • Yim, Seon-Hee;Jung, Kyu-Won;Won, Young-Joo;Kong, Hyun-Joo;Shin, Hai-Rim
    • Journal of Preventive Medicine and Public Health
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    • v.41 no.1
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    • pp.17-22
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    • 2008
  • Objectives : Period analysis estimates up-to-date survival rates of cancer patients. In this approach, analysis is restricted to recent time period by left-truncating all observations at the beginning of the period and right-censoring at its end. Here, we applied period analysis to examine changes in 5-year relative survival (RS) by age group for 1997 and for 2002. Methods : Using the National Cancer Incidence Database, 5-year RS was estimated for 1997 and 2002 in four age groups (15-54, 55-64, 65-74, and 75 years old and over) using period analysis. After excluding death certificate-only cases, patients with an unknown date of diagnosis or follow-up length, a total of 813,889 patients diagnosed with a first primary invasive cancer during 1992 2002 were included for analysis. Followup for vital status was included until 31 December 2002. Results : Five-year RS increased from 41.7% for 1997 to 46.7% for 2002. Increases in survival occurred in all age groups except in the 75 and over group. Conclusions : The age gradient in cancer prognosis seems to have widened between 1997 and 2002, a finding that requires further study of prognostic factors, including stage at diagnosis. Period analysis accurately estimates survival rates, especially for cancers with better prognosis.

The Estimation of Domestic Construction Technology Full-Text Services using Tobit Model (Tobit 모형을 이용한 국내 건설기술 원문서비스 가치 추정)

  • Jeong, Seong-Yun
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.17 no.6
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    • pp.656-662
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    • 2016
  • We have provided a variety of domestic construction technology related full-text services through the Construction Technology Digital Library system since 2001. CODIL is a system that services the database related to construction technology data. On the other hand, there is growing demand for DB every year, but the required budget is shrinking. Therefore, this study investigated the satisfaction to effectively service the construction technique-related full-text with a limited budget. The monetary value of full-text to express satisfaction with the quantified value was estimated using the Tobit model. The Tobit model is used as a contingent valuation method to estimate the value of non-market goods. This model is the limited dependent variable regression model to observations by censoring the limit of the left side or right side so that a biased outlier is not reflected in the willingness to pay. A survey was conducted by sampling 312 respondents. The mean, median, truncating the willingness of payment were calculated for the six types of the full-text services using the Tobit model. The statistically significant variables affecting the willingness to pay for the full-text services were identified. The mean value of per the full-text service was estimated to be 46,530 won. The significance of this study was to use the Tobit model to estimate the value of the construction technology-related full-text services for the first time in Korea.