• Journal of Korean Society for Quality Management
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• v.18 no.1
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• pp.9-20
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• 1990

The purpose of this paper is to propose the modified semiparametric estimators for survival function in the Cox's regression model with randomly censored data based on Tsiatis and Breslow estimators, and present their asymptotic variances estimates. The proposed estimators are compared to Tsiatis, Breslow, and Kaplan-Meier estimators through a small-sample Monte Carlo study. The simulation results show that the proposed estimators are preferred for small sample sizes.

• Korean Journal of Social Welfare
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• v.39
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• pp.210-237
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• 1999

The primary purpose of this study is to empirically examine the determinants of reemployment of the unemployed after the crash of Korea's economy in 1997. This study also investigates the effects of the government unemployment programs on reemployment of the program beneficiaries. Using the data from the 1998 Survey on Unemployment Condition and Welfare Needs, co-directed by the Korea Institute of Health and Welfare and the Korea Institute of Labor Policy, a Cox regression analysis was conducted. The study results suggested that, in general, the government unemployment programs did not have noticeable effects on reemployment of the beneficiaries. The study, however, found that the effect of the government programs varied, depending on the mode of unemployment-exit, that is, full-time versus part-time reemployment. In addition, the effects of such factors on reemployment as socio-economic characteristics of the unemployed, characteristics of households with unemployed family members, and previous job characteristics are also examined. Based on the study findings, some policy implications are discussed, and suggestions are made for improving the current unemployment programs.

• Korean Business Review
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• v.14
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• pp.45-62
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• 2001

This study examines the factors that affect longevity of strategic alliances, highlighting environmental volatility, nationality, and previous experience with strategic alliances. In general, successful strategic alliances are more likely to continue to exist than unsuccessful ones. Therefore, it is argued that studying on factors affecting the continuance of strategic alliances indirectly confirms the factors of success and failure in strategic alliances. In order to conduct this study, the needed data were collected from CATI(Cooperative Agreements and Technology Indicators) Data Base, which was gathered by a group of researchers in the University of Limburg in the Netherlands. Cox's Regression was used to analyze the data. Implications for research and practice are discussed.

• Journal of Korea Planning Association
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• v.54 no.2
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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.

• Journal of the Korean Statistical Society
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• v.20 no.1
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• pp.85-92
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• 1991

A set of conditions ensuring local asymptotic normality for independent but not necessarily identically distributed observations in semiparametric models is presented here. The conditions are turned out to be more direct and easier to verify than those of Oosterhoff and van Zwet(1979) in semiparametric models. Examples considered include the simple linear regression model and Cox's proportional hazards model without censoring where the covariates are not random.

• Journal of Labour Economics
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• v.26 no.3
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• pp.181-207
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• 2003

The purpose of this study was to conduct a dynamic analysis of married women's return to the workforce following first childbirth. We have based our investigation on the data compiled by the KLIPS, where the workforce performance is the focal point of it's research, and by these materials, this study has analyzed the aspects of the factors that decide post-childbirth return to the workforce. We have applied the Cox Regression Hazard Model, where corroborative evidence are statistically applied. The following are the conclusions that were derived from this research: First, according to the study, academic background is a vital factor in reducing the gap and time of women's return to the workforce. Second, whether having active child-care after giving birth or not doubles the chances of women returning to the workforce. Third, if the pre-birth employment form was a wage-work and the rate of returning to the workforce was lower than the non-wage, relatively speaking, this reflects that the non-wage form of work, which provides a better possibility to return to the workforce after giving birth, could be another way to prevent women's career discontinuation.

• The Journal of Advanced Prosthodontics
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• v.14 no.4
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• pp.223-235
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• 2022

PURPOSE. To compare the clinical outcomes of two types of implant restoration for posterior edentulous area, 3-unit bridge supported by 2 implants and 3 implant-supported splinted crowns. MATERIALS AND METHODS. The data included 127 implant-supported fixed restorations in 85 patients: 37 restorations of 3-unit bridge supported by 2 implants (2-IB), 37 restorations of 3 implant-supported splinted crowns (3-IC), and 53 single restorations (S) as controls. Peri-implantitis and mechanical complications that occurred for 14 years were analyzed by multivariable Cox regression model. Kaplan-Meier curves and the multivariable Cox regression model were used to analyze the success and survival of implants. RESULTS. Peri-implantitis occurred in 28.4% of 2-IB group, 37.8% of 3-IC group, and 28.3% of S control group with no significant difference. According to the implant position, middle implants (P2) of the 3-IC group had the highest risk of peri-implantitis. The 3-IC group showed a lower mechanical complication rate (7.2%) than the 2-IB (16.2%) and S control group (20.8%). The cumulative success rate was 52.8% in S (control) group, 62.2% in 2-IB group, and 60.4% in 3-IC group. The cumulative survival rate was 98.1% in S (control) group, 98.6% in 2-IB group, and 95.5% in 3-IC group. There was no significant difference in the success and survival rate according to the restoration type. CONCLUSION. The restoration type was not associated with the success and survival of implants. The risk of mechanical complications was reduced in 3 implant-supported splinted crowns. However, the middle implants of the 3 implant-supported splinted crowns had a higher risk of peri-implantitis.

• The Transactions of the Korea Information Processing Society
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• v.13 no.6
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• pp.260-268
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• 2024

Cervical cancer is the fourth most common cancer in women worldwide, and more than 604,000 new cases were reported in 2020 alone, resulting in approximately 341,831 deaths. The Cox regression model is a major model widely adopted in cancer research, but considering the existence of nonlinear associations, it faces limitations due to linear assumptions. To address this problem, this paper proposes ResSurvNet, a new model that improves the accuracy of cervical cancer mortality prediction using ResNet's residual learning framework. This model showed accuracy that outperforms the DNN, CPH, CoxLasso, Cox Gradient Boost, and RSF models compared in this study. As this model showed accuracy that outperformed the DNN, CPH, CoxLasso, Cox Gradient Boost, and RSF models compared in this study, this excellent predictive performance demonstrates great value in early diagnosis and treatment strategy establishment in the management of cervical cancer patients and represents significant progress in the field of survival analysis.

• Asian Pacific Journal of Cancer Prevention
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• v.16 no.17
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• pp.7463-7466
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• 2015

Aims: To analyse the predictors of recurrence, disease free survival and overall survival in cases with endometrial cancer. Materials and Methods: A total of 152 women diagnosed with endometrial cancer were screened using a prospectively collected database including age, smoking history, menopausal status, body mass index, CA125, systemic disorders, tumor histology, tumor grade, lymphovascular space invasion, tumor diameter, cervical involvement, myometrial invasion, adnexal metastases, positive cytology, serosal involvement, other pelvic metastases, type of surgery, fertility sparing approach to assess their ability to predict recurrence, disease free survival and overall survival. Results: In ROC analyses tumor diameter was a significant predictor of recurrence (AUC:0.771, P<0.001). The optimal cut off value was 3.75 with 82% sensitivity and 63% specificity. In correlation analyses tumor grade (r=0.267, p=0.001), tumor diameter (r=0.297, p<0.001) and the serosal involvement (r=0.464, p<0.001) were found to significantly correlate with the recurrence. In Cox regression analyses when some different combinations of variables included in the model which are found to be significantly associated with the presence of recurrence, tumor diameter was found to be a significant confounder for disease free survival (OR=1.2(95 CI,1.016-1.394, P=0.031). On Cox regression for overall survival only serosal involvement was found to be a significant predictor (OR=20.8 (95 % CI 2.4-179.2, P=0.006). In univariate analysis of tumor diameter > 3.75 cm and the recurrence, there was 14 (21.9 %) cases with recurrence in group with high tumor diameter where as only 3 (3.4 %) cases group with smaller tumor size (Odds ratio:7.9 (95 %CI 2.2-28.9, p<0.001). Conclusions: Although most of the significantly correlated variables are part of the FIGO staging, tumor diameter was also found to be predictor for recurrence with higher values than generally accepted.

• Journal of Korean Society for Quality Management
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• v.42 no.3
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• pp.361-372
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• 2014

Purpose: In this paper, we investigate whether the endeavors for 6 sigma quality management by a firm have positive effects on its financial performance and the length of 6 sigma implemented period affects its financial status. Methods: We conduct the analysis using the data from Workplace Panel Survey 2009. We use multiple linear regression in order to analyze the relationship between the efforts for quality management and financial performance. Specifically, the return on assets (ROA) and return on equity (ROE) are investigated as dependent variables and the efforts for quality management as independent variable. The Box-Cox transformation and Cook's distance are also used. Results: As a result of the analysis, the indication is that companies that put effect into the six sigma quality management have a positive result in its financial status. In detail, the efforts for six sigma quality management have positive effects on total asset turnover ratio and six sigma implemented period on net income to net sales ratio. Additionally, companies with longer(shorter) period of six sigma program have more (less) improvement in its financial status. Conclusion: It can be concluded that the company's efforts for quality management positively influence financial performance.