• Title, Summary, Keyword: log-rank test

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Comparison of Trend Tests for Genetic Association on Censored Ages of Onset (미완결 발병연령에 근거한 연관성 추세 검정법의 비교)

  • Yoon, Hye-Kyoung;Song, Hae-Hiang
    • The Korean Journal of Applied Statistics
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    • v.21 no.6
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    • pp.933-945
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    • 2008
  • The genetic association test on age of onset trait aims to detect the putative gene by means of linear rank tests for a significant trend of onset distributions with genotypes. However, due to the selective sampling of recruiting subjects with ages less than a pre-specified limit, the genotype groups are subject to substantially different censored distributions and thus this is one reason for the low efficiencies in the linear rank tests. In testing the equality of two survival distributions, log-rank statistic is preferred to the Wilcoxon statistic, when censored observations are nonignorable. Therefore, for more then two groups, we propose a generalized log-rank test for trend as a genetic association test. Monte Carlo studies are conducted to investigate the performances of the test statistics examined in this paper.

Weighted log rank test for late differences (후기 차이 검출을 위한 가중 로그 순위 검정)

  • Gyu Jin Jeong;Sang Gue Park
    • The Korean Journal of Applied Statistics
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    • v.7 no.2
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    • pp.79-88
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    • 1994
  • Weighted log rank test is a widely applicable test when one is interested in detecting the differences between two groups. In man clinical trials it is common to see no differences in early experiments and does show significant differences later. We propose new weighted log rank test and illustrate it through an example. We also examine the empirical powers and show that the proposed test is more sensitive to detect late differences.

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Prognostic Influence of Preoperative Fibrinogen to Albumin Ratio for Breast Cancer

  • Hwang, Ki-Tae;Chung, Jung Kee;Roh, Eun Youn;Kim, Jongjin;Oh, Sohee;Kim, Young A;Rhu, Jiyoung;Kim, Suzy
    • Journal of Breast Cancer
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    • v.20 no.3
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    • pp.254-263
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    • 2017
  • Purpose: Elevated serum concentration of fibrinogen and decreased serum concentration of albumin have been reported to be markers of elevated systemic inflammation. We attempted to investigate the prognostic influence of preoperative fibrinogen to albumin ratio (FAR) for breast cancer. Methods: Data from 793 consecutive primary breast cancer patients were retrospectively analyzed. Serum levels of fibrinogen and albumin were tested before curative surgery. Subjects were grouped into two groups according to the cutoff value determined by performing the receiver operating characteristic curve analysis: the high FAR group (FAR>7.1) and the low FAR group ($FAR{\leq}7.1$). Overall survival was assessed using the Kaplan-Meier estimator. Independent prognostic significance was analyzed using the Cox proportional hazards model. Results: The high FAR group had a worse prognosis compared to the low FAR group (log-rank test, p<0.001). The prognostic effect of FAR was more significant than that of single markers such as fibrinogen (log-rank test, p=0.001) or albumin (log-rank test, p=0.001). The prognostic effect of FAR was prominent in the stage II/III subgroup (log-rank test, p<0.001) and luminal A-like subtype (log-rank test, p<0.001). FAR was identified as a significant independent factor on both univariate (hazard ratio [HR], 2.722; 95% confidence interval [CI], 1.659-4.468; p<0.001) and multivariate analysis (HR, 2.622; 95% CI, 1.455-4.724; p=0.001). Conclusion: Preoperative FAR was a strong independent prognostic factor in breast cancer. Its prognostic effect was more prominent in the stage II/III subgroup and in the luminal A-like subtype. Therefore, preoperative FAR can be utilized as a useful prognosticator for breast cancer patients. Further studies are needed to validate its applications in clinical settings.

A comparison of the statistical methods for testing the equality of crossing survival functions (교차하는 두 생존함수의 동일성 검정법에 관한 비교연구)

  • Lee, Youn Ju;Lee, Jae Won
    • Journal of the Korean Data and Information Science Society
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    • v.26 no.3
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    • pp.569-580
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    • 2015
  • Log-rank is widely used for testing equality of two survival functions, and this method is efficient only under the proportional hazard assumption. However, crossing survival functions are common in practice. Therefore, many approaches have been suggested to test equality of them. This study considered several methods; Renyi type test, modified Kolmogorov-Smirnov and Cramer-von Mises test, and weighted Log-rank test, which can be applied when the survival functions cross, and simulated power of those methods. Based on the simulation results, we provide the useful information to choose a suitable approach in a given situation.

Bayesian test for the differences of survival functions in multiple groups

  • Kim, Gwangsu
    • Communications for Statistical Applications and Methods
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    • v.24 no.2
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    • pp.115-127
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    • 2017
  • This paper proposes a Bayesian test for the equivalence of survival functions in multiple groups. Proposed Bayesian test use the model of Cox's regression with time-varying coefficients. B-spline expansions are used for the time-varying coefficients, and the proposed test use only the partial likelihood, which provides easier computations. Various simulations of the proposed test and typical tests such as log-rank and Fleming and Harrington tests were conducted. This result shows that the proposed test is consistent as data size increase. Specifically, the power of the proposed test is high despite the existence of crossing hazards. The proposed test is based on a Bayesian approach, which is more flexible when used in multiple tests. The proposed test can therefore perform various tests simultaneously. Real data analysis of Larynx Cancer Data was conducted to assess applicability.

A Test Procedure for Right Censored Data under the Additive Model

  • Park, Hyo-Il;Hong, Seung-Man
    • Communications for Statistical Applications and Methods
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    • v.16 no.2
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    • pp.325-334
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    • 2009
  • In this research, we propose a nonparametric test procedure for the right censored and grouped data under the additive hazards model. For deriving the test statistics, we use the likelihood principle. Then we illustrate proposed test with an example and compare the performance with other procedure by obtaining empirical powers. Finally we discuss some interesting features concerning the proposed test.

On Best Precedence Test when Data are subject to Unequal Patterns of Censorship

  • Kim, Tai-Kyoo;Park, Sang-Gue
    • Journal of the Korean Society for Quality Management
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    • v.22 no.1
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    • pp.169-178
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    • 1994
  • Nonparametric tests for comparing two treatments when data are subject to unequal patterns of censorship are discussed. Best precedence test proposed by Slud can be viewed as a nice alternative test comparing with weighted log-rank tests, not to mention the advantage of short experimental period. This research revises some missing parts of Slud's test and examines the asymptotic power of it under the nonproportional hazard alternatives through the simulation. The simulation studies show best precedence test has reasonable power in the sense of robustness under nonproportional hazard alternatives and could be recommended at such situation.

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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.

NONPARAMETRIC ONE-SIDED TESTS FOR MULTIVARIATE AND RIGHT CENSORED DATA

  • Park, Hyo-Il;Na, Jong-Hwa
    • Journal of the Korean Statistical Society
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    • v.32 no.4
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    • pp.373-384
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    • 2003
  • In this paper, we formulate multivariate one-sided alternatives and propose a class of nonparametric tests for possibly right censored data. We obtain the asymptotic tail probability (or p-value) by showing that our proposed test statistics have asymptotically multivariate normal distributions. Also, we illustrate our procedure with an example and compare it with other procedures in terms of empirical powers for the bivariate case. Finally, we discuss some properties of our test.

A Comparison of Testing Methods for Equality of Survival Distributions with Interval Censored Data

  • Kim, Soo-Hwan;Lee, Shin-Jae;Lee, Jae-Won
    • The Korean Journal of Applied Statistics
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    • v.25 no.3
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    • pp.423-434
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    • 2012
  • A two-sample test for equality of survival distribution is one of the important issues in survival analysis, especially for clinical and epidemiological research. With interval censored data, some testing methods have been developed. This study introduces some testing methods and compares them under various situations through simulation study. Based on simulation result, it provides some useful information on choosing the most appropriate testing method in a given situation.