• The Korean Journal of Applied Statistics
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• v.37 no.2
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• pp.225-237
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• 2024

In the analysis of competing risks data, some of covariates may not be fully observed for some subjects. In such cases, excluding subjects with missing covariate values from the analysis may result in biased estimates and loss of efficiency. In this paper, we studied multiple imputation and the augmented inverse probability weighting method for regression parameter estimation in the cause-specific proportional hazards model with missing covariates. The performance of estimators obtained from multiple imputation and the augmented inverse probability weighting method is evaluated by simulation studies, which show that those methods perform well. Multiple imputation and the augmented inverse probability weighting method were applied to investigate significant risk factors for the risk of death from breast cancer and from other causes for breast cancer data with missing values for tumor size obtained from the Prostate, Lung, Colorectal, and Ovarian Cancer Screen Trial Study. Under the cause-specific proportional hazards model, the methods show that race, marital status, stage, grade, and tumor size are significant risk factors for breast cancer mortality, and stage has the greatest effect on increasing the risk of breast cancer death. Age at diagnosis and tumor size have significant effects on increasing the risk of other-cause death.

• 한국노년학
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• v.37 no.4
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• pp.871-891
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• 2017

The purpose of this paper is to reduce the reverse-causality and overestimate bias of analysis on how health affected middle-aged and elderly worker's early retirement. From the Korean Longitudinal Study of Ageing(KLoSA) panel data, I researched 1,049 people who were 45-52 years old in 2006. To eliminate the reverse-causality problem, I used the health data which is surveyed before retirement. To reduce bias, I controlled the health status when retirees worked. The main results are as follows. First, the worsened health still affects the hazard of early retirement, with reducing the endogeneity problem. Second, chronic illness is one of the strong predictors of early retirement to self-employed, and self-reported bad health is the main health predictor of wage workers. These results give two implications; first, the impact magnitude of the health indicator depends on employment type. Each employment type has different flexibility of working hours. It seems that the flexibility can reduce early retirement hazard with health problems. Self-employed, who has more flexibility of working hours can work until they have to stop working due to the serious health problem or doctor's advice. Second, to promote middle-aged and elderly workers to keep working, the long-term health policy which decreases chronic illness is needed.

• 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.