• Communications for Statistical Applications and Methods
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• 제17권1호
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• pp.117-126
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• 2010

Clinical researchers often analyze survival data as binary outcomes using the logistic regression method. This paper examines the information loss resulting from analyzing survival time as binary outcomes. We first demonstrate that, under the proportional hazard assumption, this binary discretization does result in a significant information loss. Second, when fitting a logistic model to survival time data, researchers inadvertently use the maximal statistic. We implement a numerical study to examine the properties of the reference distribution for this statistic, finally, we show that the logistic regression method can still be a useful tool for analyzing survival data in particular when the proportional hazard assumption is questionable.

• 한국수자원학회논문집
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• 제42권6호
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• pp.445-455
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• 2009

본 논문에서는 연구대상 지역의 150 mm 주철 상수관로의 첫 번째 파손으로부터 일곱 번째 파손사건에 대한 비례 위험모형을 구축하였다. 모형의 구축과정에서 공변수의 위험률에 대한 비례위험 가정을 검사하여 이를 위배할 경우 시간종속형 공변수로 모형화하였다. 그 결과 첫 번째 파손에 대해서는 관로의 제원 및 연결 방식과 급수인구가, 그리고 두 번째 파손 사건에 대해서는 급수인구의 영향이 시간에 따라 변하는 것으로 나타났다. 각 생존시간군의 기저위험률에 대한 분석으로부터 첫 번째와 두 번째 파손에 대해서는 대체적으로 파손 위험률이 시간에 따라 계속해서 증가하는 것으로 나타났으며, 세 번째 파손으로부터 일곱번째 파손사건에 대해서는 파손 위험률이 감소하다가 시간이 지나면 증가하는 욕조 모양으로 추정되었다. 또한 시간과 파손횟수에 따른 기저위험률의 변화 및 각 생존시간군의 중간생존시간으로부터 연구대상 상수관로들은 파손횟수가 증가할수록 전반적인 관로의 상태가 악화되는 것으로 판단된다. 추정된 공변수의 회귀계수와 위험비율을 이용하여 관로파손에 미치는 인자와 그 시간적 영향에 대하여 분석하였으며, 구축된 모형의 이탈잔차를 이용하여 모형의 적합도를 검증하였다.

• 중환자간호학회지
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• 제3권2호
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• pp.1-11
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• 2010

Purpose: This study was designed to identify the factors affecting healing of Stage 2 pressure ulcer in an acute care facility in Korea. Methods: 286 Stage 2 pressure ulcers of 145 patients were examined. Data were collected in the period between October $1^{st}$, 2006 and September $30^{th}$, 2007. Data were analyzed with Kaplan-Meier survival analysis for cumulative recovery rate of Stage 2 pressure ulcers. Cox proportional hazard model was used to examine effects of multiple variables simultaneously. Results: Out of 286 initial Stage 2 pressure ulcers, 204 (71.3%) pressure ulcers healed completely. The median time to heal was 15 days according to Kaplan-Meier survival analysis. Cox proportional hazard model showed that the Stage 2 pressure ulcers healed more quickly when pressure redistribution surfaces were used (p<.001, HR=2.184), patients were administered with vitamins (p= .038, HR=1.451), and the size of the pressure ulcers were small (${\leq}3.0cm^2$, p= .006, HR=1.765). Conclusion: The factors contributing to the healing of Stage 2 pressure ulcer in an acute care setting were the application of pressure redistribution surface, small ulcer size (${\leq}3.0cm^2$), and the administration of vitamins.

• Journal of the Korean Data and Information Science Society
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• 제21권2호
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• pp.201-209
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• 2010

최근 10년간 허혈성심질환 사망은 급격히 증가하였기에 이에 대한 효과적인 예방대책이 매우 중요한 실정이다. 이에 본 연구에서는 1996년 국민건강보험공단 건강검진 수검자 2,268,018명을 약 10년간 추적하여 허혈성심질환의 주요 위험요인별 상대위험도를 콕스비례위험모형을 통해 파악하고자 하였다. 그 결과 남자에서는 체질량지수, 혈압, 흡연, 여자에서는 고혈압, 주관적 건강감 및 감마-글루타밀전이효소가 허혈성심질환과 유의한 관련성이 있었다.

• 국토계획
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• 제54권2호
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• pp.5-16
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• 2019

The purpose of this study is to analyze the spatial characteristics of business-type-changed parcel in the Hongik-University commercial area, from the view point of commercial gentrification. A commercial gentrification occurs through a business-type-change in a spatial basic unit (microscopic spatial unit such as parcel) of an area which has not been considered in relavent policies and research. So, this study analyzed the spatial characteristics of business-type-changed parcels using the Cox's proportional hazard regression model. The main results of this study are as follows. First, as new developments in the adjacent area occur, the business-type-change probability increases. Second, by the commercial area division, the business-type-change probability is different. Finally, the accessibility is better, the probability is higher. These results could suggest that a consideration of the spatial characteristics form microscopic viewpoint is necessary to understand the commercial gentrification. And these could be used as basic data for a gentrification diagnostic and management system, which can predict gentrification from the view point of business-type-change on the basis of a parcel.

• Asian Pacific Journal of Cancer Prevention
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• 제15권21호
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• pp.9453-9458
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• 2014

Background: Breast cancer is the second leading cause of cancer death for women in the United States. Differences in survival of breast cancer have been noted among racial and ethnic groups, but the reasons for these disparities remain unclear. This study presents the characteristics and the survival curve of two racial and ethnic groups and evaluates the effects of race on survival times by measuring the lifetime data-based half-normal model. Materials and Methods: The distributions among racial and ethnic groups are compared using female breast cancer patients from nine states in the country all taken from the National Cancer Institute's Surveillance, Epidemiology, and End Results cancer registry. The main end points observed are: age at diagnosis, survival time in months, and marital status. The right skewed half-normal statistical probability model is used to show the differences in the survival times between black Hispanic (BH) and black non-Hispanic (BNH) female breast cancer patients. The Kaplan-Meier and Cox proportional hazard ratio are used to estimate and compare the relative risk of death in two minority groups, BH and BNH. Results: A probability random sample method was used to select representative samples from BNH and BH female breast cancer patients, who were diagnosed during the years of 1973-2009 in the United States. The sample contained 1,000 BNH and 298 BH female breast cancer patients. The median age at diagnosis was 57.75 years among BNH and 54.11 years among BH. The results of the half-normal model showed that the survival times formed positive skewed models with higher variability in BNH compared with BH. The Kaplan-Meir estimate was used to plot the survival curves for cancer patients; this test was positively skewed. The Kaplan-Meier and Cox proportional hazard ratio for survival analysis showed that BNH had a significantly longer survival time as compared to BH which is consistent with the results of the half-normal model. Conclusions: The findings with the proposed model strategy will assist in the healthcare field to measure future outcomes for BH and BNH, given their past history and conditions. These findings may provide an enhanced and improved outlook for the diagnosis and treatment of breast cancer patients in the United States.

• International Journal of Reliability and Applications
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• 제9권1호
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• pp.113-122
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• 2008

In this paper, we consider a periodic preventive maintenance policy in which each preventive maintenance reduces the hazard rate of amount proportional to the failure intensity, which increases since the system started to operate. And the effect of preventive maintenance at each preventive maintenance epoch is different. The expected cost rate per unit time for the proposed model is obtained. We discuss the optimal number N of the periodic preventive maintenance and the optimal period x, which minimize the expected cost rate per unit time and obtain the optimal preventive maintenance schedule for given cost structures of the model. A numerical example is given for the purpose of illustrating our results when the failure time distribution is Weibull distribution.

• Journal of the Korean Data and Information Science Society
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• 제27권2호
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• pp.285-294
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• 2016

취업자들이 재직기간이 경과하면서 이직 또는 실업 상태로 탈출확률 및 탈출요인 문제를 분석하는 것은 취업의 질을 측정할 수 있는 하나의 방법이다. 일반적으로 취업자들의 이직 또는 실업으로의 탈출확률은 취업자의 개인특성뿐만 아니라, 직종 특성에도 영향을 받는 복수의 분석단위를 가지게 된다. 복수의 분석단위를 가지는 위계적 (hierarchical) 자료구조에서는 직종별로 공유되는 특성이 존재하게 되어, 동일 직종 집단 내의 상관이 발생할 수 있다. 따라서 본 연구에서는 취업자 개인특성 (1-수준)과 직종 특성 (2-수준)의 위계적 자료구조 하에서 콕스의 비례위험 모형 (Cox's proportional hazard model)을 이용하여 중소기업 청년인턴사업에 참여한 취업자들의 재직기간 중 실직 및 이직으로의 탈출요인을 분석하였다. 분석결과를 요약하면 다음과 같다. 처리집단 (인턴집단)이 통제집단 (비인턴집단)에 비해서 탈출확률이 통계적으로 유의하게 낮음을 알 수 있다. 또한 남자들이 여자들에 비해서 탈출할 확률이 높고, 연령이 높을수록 탈출할 확률이 더 낮아지는 것을 알 수 있다. 그리고 기업규모가 클수록 탈출확률이 낮으며, 직종별로는 관리사무 관련직에 비해서 전문 서비스 관련직의 탈출확률이 더 낮게 나타났다.

• 한국통계학회:학술대회논문집
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• 한국통계학회 2005년도 춘계 학술발표회 논문집
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• pp.17-23
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• 2005

In this paper we consider the well-known semiparametric proportional hazards models for survival analysis. These models are usually used with few covariates and many observations (subjects). But, for a typical setting of gene expression data from DNA microarray, we need to consider the case where the number of covariates p exceeds the number of samples n. For a given vector of response values which are times to event (death or censored times) and p gene expressions(covariates), we address the issue of how to reduce the dimension by selecting the significant genes. This approach enables us to estimate the survival curve when n ${\ll}$p. In our approach, rather than fixing the number of selected genes, we will assign a prior distribution to this number. The approach creates additional flexibility by allowing the imposition of constraints, such as bounding the dimension via a prior, which in effect works as a penalty To implement our methodology, we use a Markov Chain Monte Carlo (MCMC) method. We demonstrate the use of the methodology to diffuse large B-cell lymphoma (DLBCL) complementary DNA (cDNA) data and Breast Carcinomas data.

• 농촌의학ㆍ지역보건
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• 제32권1호
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• pp.13-26
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• 2007

Objectives: This study was conducted to investigate the association between health risk factors and mortality in Juam cohort. Methods: The subjects were 1,447 males and 1,889 females who had been followed up for 68.5 months to 1 January 2001. Whether they were alive or not was confirmed by the mortality data of the National Statistical Office. A total of 289 persons among them died during the follow-up period. The Cox's proportional hazard regression model was used for survival analysis. Results: Age, type of medical insurance, self cognitive health level, habit of alcohol drinking, smoking, exercise and BMI level were included in Cox's proportional hazard model by gender. The hazard ratio of age was 1.07(95% CI: 1.05-1.10) in men, 1.09(95% CI: 1.06-1.12) in women. The hazard ratio of medical aid(lower socioeconomic state) was 1.43(95% CI 1.02-2.19) in women. The hazard ratios of current alcohol drinking and current smoking were respectively 1.69(95% CI: 1.01-2.98), 1.52(95% CI: 1.02-2.28) in women. The hazard ratio of underweight was 1.56(95% CI 1.08-2.47) in men. The hazard ratios of underweight, normoweight, overweight, and obesity were respectively 1.63(95% CI: 1.02-2.67), 1.0(referent), 0.62(95% CI: 0.32-1.63), 1.27(95% CI: 0.65-3.06), which supported the U-shaped relationship between body mass index and mortality among the men over 65. Conclusions: The health risk factors increasing mortality were age, underweight in male, age, lower socioeconomic state, current alcohol drinking, current smoking in female. To evaluate long-term association between health risk factors and mortality, further studies need to be carried out.