• 한국유기농업학회지
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• 제24권2호
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• pp.169-188
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• 2016

The purpose of this study is to analyze willingness to pay (WTP) for organic agricultural products. To accomplish the objective of the study, a consumer survey was conducted. Based on the pilot survey results, parametric survival model was used to analyze the WTP for organic products. The estimation results showed that the WTP for organic agricultural products is 1.4-fold when compared with the conventional products, which is lower than the current price by about 30 percent. The analytical results also showed that such variables as gender, recognitions for organic agricultural products, and consumers' income have very significant effects on the WTP, and that there are no differences among WTPs by consumption goals. Based on major findings, the most effective countermeasure was suggested for expanding of organic food consumption through the premium reduction of organic products. Reducing the costs of production and distribution, supporting farmers' income by direct payment system were presented. Furthermore, it is needed to allocate more budget for promoting the consumption and distribution of organic agricultural products, and for enhancing conservation of agricultural environment.

• Journal of the Korean Data and Information Science Society
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• 제26권6호
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• pp.1225-1238
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• 2015

본 연구에서는 직장암 환자들의 수술 후 재발까지의 시간 데이터에 대해 집단 간 생존함수 양상에 차이가 있는지 로그 순위 검정 결과 유의수준 10%에서 포도당 단일수송체 (GLUT1)의 수준, 수술 전 병기 (cstage), 수술 후 병기 (ypstage)에 따른 차이가 유의하며, Cox 비례위험률 모형을 이용하여 검정한 결과 가장 유의한 공변량은 포도당 단일수송체와 수술 후 병기였다. 지수분포를 따른다고 가정할 경우, 우도함수를 기반한 여러 가지 위험률 변화점을 추정하였다.

• Asian Pacific Journal of Cancer Prevention
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• 제17권sup3호
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• pp.311-316
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• 2016

Breast cancer is one of the most common causes of cancer mortality in Iran. Social determinants of health are among the key factors affecting the pathogenesis of diseases. This cross-sectional study aimed to determine the social determinants of breast cancer survival time with parametric and semi-parametric regression models. It was conducted on male and female patients diagnosed with breast cancer presenting to the Cancer Research Center of Shohada-E-Tajrish Hospital from 2006 to 2010. The Cox proportional hazard model and parametric models including the Weibull, log normal and log-logistic models were applied to determine the social determinants of survival time of breast cancer patients. The Akaike information criterion (AIC) was used to assess the best fit. Statistical analysis was performed with STATA (version 11) software. This study was performed on 797 breast cancer patients, aged 25-93 years with a mean age of 54.7 (${\pm}11.9$) years. In both semi-parametric and parametric models, the three-year survival was related to level of education and municipal district of residence (P<0.05). The AIC suggested that log normal distribution was the best fit for the three-year survival time of breast cancer patients. Social determinants of health such as level of education and municipal district of residence affect the survival of breast cancer cases. Future studies must focus on the effect of childhood social class on the survival times of cancers, which have hitherto only been paid limited attention.

• Archives of Plastic Surgery
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• 제36권4호
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• pp.411-416
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• 2009

Purpose: Malignant melanoma is recognized as the most serious skin cancer. We examined anatomical distribution and 5 - year survival rate of each stage of malignant melanoma on lower leg. Methods: We retrospectively analyzed the medical records of 91 patients(46 males and 45 females) with malignant melanoma on lower leg from 1985 to 2008. Age, sex, anatomical distribution and 5 - year survival rates of each stage of malignant melanoma on lower leg were investigated. Also, 5 - year survival rates of each stage and invasion depth of malignant melanoma on heel pad were investigated. Results: On lower leg, most frequently 32 cases(35.1%) occurred on heel pad, 27 cases(29.7%) occurred on dorsum of foot, 18 cases(19.8%) in toe and 14 cases(15.4%) on others in lower leg. We used the excision margin as 3 ~ 5 cm. After wide excision, in stage III, IV, the patients underwent the immunologic / chemo - therapy. The incidences of each stage were 22 cases(24.2%) in stage I, 47(51.6%) in II, 17(18.7%) in III and 5(5.5%) in IV. The 5 - year survival rates of each stage were 85%, 53.2%, 47.1% and 40%. On heel pad, the incidences of each stage were 5 cases(15.6%) in stage I, 19 cases(59.4%) in II, 7 cases(21.9%) in III and 1 case(3.1%) in IV. The 5 - year survival rates of each stage were 80%, 63.2%, 42.9% and 100%. On heel pad, incidence of local recurrence was 2 and 5 - year survival rate of this case was 100%. And systemic recurrence was 9 and 5 - year survival rate of this case was 55.6%. Conclusion: The 5 - year survival rate of malignant melanoma on heel pad was higher than previous study. To maintain the weight - bearing function of foot, we recommend the active reconstructive surgery for heel pad reconstruction after wide excision of heel pad malignant melanoma.

• Communications for Statistical Applications and Methods
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• 제14권1호
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• pp.111-119
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• 2007

In this paper, we develop a nonparametric Bayesian methodology of estimating an unknown distribution function F at the given survival time with current status data under the assumption of Dirichlet process prior on F. We compare our algorithm with the nonparametric maximum likelihood estimator through application to simulated data and real data.

• Communications for Statistical Applications and Methods
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• 제9권3호
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• pp.825-834
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• 2002

Poisson processes are widely used in reliability and survival analysis. In particular, multiple event time data in survival analysis are routinely analyzed by use of Poisson processes. In this paper, we consider large sample properties of nonparametric Bayesian models for Poisson processes. We prove that the posterior distribution of the cumulative intensity function of Poisson processes is consistent under regularity conditions on priors which are Levy processes.

• Journal of the Korean Statistical Society
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• 제30권1호
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• pp.127-138
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• 2001

In order to combine parametric and nonparametric approaches together for survival analysis with censored observations, a new class of priors called mixtures of the beta processes is introduced. It is shown that mixtures of beta processes priors generalized the well known priors - mixtures of Dirichlet processes, and they are conjugate with right censored observations. Formulas for computing the posterior distribution are derived. Finally, a real data set is analyzed for illustrational purpose.

• Communications for Statistical Applications and Methods
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• 제9권1호
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• pp.261-270
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• 2002

In this paper, we demonstrate the more accurate confidence intervals for median survival time under the simple proportional hazard model of Koziol and Green (1976) via the Edgeworth expansion for the distribution of the studentized ACL estimator derived in Jeong (2000). The numerical results show that the intervals, so-called test-based and reflect intervals (Slud et al., 1984), outperform normal approximating method in the small sample sizes and/or heavy censoring.

• Journal of the Korean Data and Information Science Society
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• 제15권3호
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• pp.605-616
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• 2004

In this paper we consider the proportional hazard models for survival analysis in the microarray data. For a given vector of response values and gene expressions (covariates), we address the issue of how to reduce the dimension by selecting the significant genes. In our approach, rather than fixing the number of selected genes, we will assign a prior distribution to this number. To implement our methodology, we use a Markov Chain Monte Carlo (MCMC) method.

• International Journal of Reliability and Applications
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• 제2권1호
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• pp.49-56
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• 2001

In this paper we consider empirical Bayes estimation of the hazard rate and survival probabilities with right censored data under the assumption that the hazard function is constant over the period of observation and the prior distribution is gamma. We provide an estimator of the first derivative of the prior moment generating function that converges at each point to the true value in $L_2$ and use it to obtain, easy to compute, asymptotically optimal estimators under the squared error loss function.