• Journal of the Korean Data and Information Science Society
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• 제26권1호
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• pp.217-227
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• 2015

In observational study, handling confounders is a primary issue in measuring treatment effect of interest. Historically, a regression with covariate adjustment (covariate-adjusted regression) has been the typical approach to estimate treatment effect incorporating potential confounders into model. However, ever since the introduction of the propensity score, covariate-adjusted regression has been gradually replaced in medical literatures with various balancing methods based on propensity score. On the other hand, there is only a paucity of researches assessing propensity score methods compared with the covariate-adjusted regression. This paper examined the performance of propensity score methods in estimating risk difference and compare their performance with the covariate-adjusted regression by a Monte Carlo study. The study demonstrated in general the covariate-adjusted regression with variable selection procedure outperformed propensity-score-based methods in terms both of bias and MSE, suggesting that the classical regression method needs to be considered, rather than the propensity score methods, if a performance is a primary concern.

• Asian Pacific Journal of Cancer Prevention
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• 제16권14호
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• pp.5787-5792
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• 2015

Background: Reported age standardized incidence rates for esophageal cancer in Iran are 0.88 and 6.15 for females and males, at fifth and the eighth ranks, respectively, of cancers overall. The present study aimed to map relative risk using more realistic and less problematic methods than common estimators. Materials and Methods: In this ecological investigation, the studied population consisted of all esophageal cancer patients in Iran from 2005 to 2007. The Bayesian multilevel space-time model with three levels of county, province, and time was used to measure the relative risk of esophageal cancer. Analyses were conducted using R package INLA. Results: The total number of registered patients was 7,160. According to the results, the three-level model with adjustment for risk factors of physical activity and smoking had the best fit among all models. The overall temporal trend was significantly increasing. At county level, Ahar, Marand, Salmas, Bojnoord, Saghez, Sarakhs, Shahroud and Torbatejam had the highest relative risks. Physical activity was found to have significant direct association with risk of developing esophageal cancer. Conclusions: Given to great variation across geographical areas, many different factors affect the incidence of esophageal cancer. Conducting further studies at the individual level in areas with high incidence could provide more detailed information on risk factors of esophageal cancer.

• Journal of Preventive Medicine and Public Health
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• 제35권3호
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• pp.263-268
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• 2002

Objective : This study was aiming at estimating the joint effects of various risk factors associated with uterine cervix cancer in Korea. Methods : Data obtained from a case-control study were analyzed with a multiplicative model. Results : After adjustment for age and husband's educational attainments, the family history of cervical cancer (OR=2.1, 95% CI=1.2-3.9), unstable marital status due to separation, by death or divorce, etc. (OR=2.8, 95% CI=1.7-4.6), and a large number of deliveries ($\geq$3 vs. nulliparous OR=6.5, 55% CI=1.4-29.0) increased the risk of uterine cervix cancer, Conversely, first sexual intercourse at an older age ($\geq$25 years vs. <19 years OR=0.4, 95% CI=0.2-0.6) and husband's circumcision (OR=0.7, 95% CI=0.5-1.0) decreased the risk. In the multiplicative model, the highest joint risk (OR=39.2, 95% CI 5.9-258.9) was observed in women with a family history of uterine cervical cancer, an unstable marital status, where the ex-husband was not circumcised, with 3 or more delivery experiences, and having her first sexual intercourse when younger than 19 years of age. However, women without a family history of uterine cervix cancer, married to a circumcised husband, having had her first sexual intercourse at 25 years or older, and nulliparous, showed the lowest joint effect (OR=0.3, 95% CI=0.1-0.5). Conclusion : As carcinogenesis is a complex action involving various factors, we consider a joint effects approach to be appropriate in an epidemiological study on risk factors for uterine cervix neoplasms cervix neoplasm.

• The Journal of Asian Finance, Economics and Business
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• 제7권12호
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• pp.605-613
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• 2020

In unfrictionless markets, one measure of asset pricing is its height of friction. This study develops a three-factor model by loosening the assumptions about stocks without friction, without risk, and perfectly liquid. Friction is used as an indicator of transaction costs to be included in the model as a variable that will reduce individual profits. This approach is used to estimate return, beta and other variable for firms listed on the Indonesian Stock Exchange (IDX). To test the efficacy of friction-adjusted three-factor model, we use intraday data from July 2016 to October 2018. The sample includes all listed firms; intraday data chosen purposively from regular market are sorted by capitalization, which represents each tick size from the biggest to smallest. We run 3,065,835 intraday data of asking price, bid price, and trading price to get proportional quoted half-spread and proportional effective half-spread. We find evidence of adjusted friction on the three-factor model. High/low trading friction will cause a significant/insignificant return difference before and after adjustment. The difference in average beta that reflects market risk is able to explain the existence of trading friction, while the difference between SMB and HML in all observation periods cannot explain returns and the existence of trading friction.

• 한국인터넷방송통신학회논문지
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• 제16권1호
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• pp.193-198
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• 2016

안전한 플랜트 설비의 상태 감시 및 장애 진단을 위해 무선 센서를 이용한 플랜트 설비용 모니터링 시스템이 연구되고 있다. 플랜트 설비에서는 저전력 뿐만 아니라 안전사고와 직결된 긴급 상황시 실시간성도 고려해야 한다. 본 논문에서는 플랜트 시설에서 지연시간 감소를 위한 동적 듀티사이클 조절 기법을 제안한다. 제안된 동적 듀티사이클 조절 기법은 센싱된 데이터 값의 긴급한 정도에 따라 미리 정의된 위험 그룹으로 구분하여 적응적으로 듀티사이클 주기를 조절한다. 실시간성을 평가하기 위해 고정 듀티사이클 기법과 동적 듀티사이클의 예상 지연시간을 확률적으로 분석하였다. 비교 결과, 플랜트 시설과 같이 이상 징후 발생 시 에너지를 소모하더라도 실시간성을 제공해야 하는 상황에서 제안 동적 듀티사이클 기법이 더 효과적임을 확인하였다.

• 보건행정학회지
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• 제31권2호
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• pp.180-187
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• 2021

Background: This study analyzed the effect of applying the diagnosis-related group (DRG)-based payment system, which was implemented in July 2012 for hospitals and clinics nationwide, on the cesarean section rate. Methods: The subjects of the study were divided into new groups that participated in the payment system after July 2012 and maintenance groups that participated in the payment system before July 2012. As an analysis method, a difference-in-difference analysis, which is a quasi-experimental design, was used. The risk-adjusted cesarean section rate was used as a dependent variable. Results: Seven risk factors (malpresentation of fetus, eclampsia, multiple pregnancies, problems in the placenta, previous Cesarean section, cephalopelvic disproportion, problems in amniotic fluid) were included in the final risk-adjustment model, and found to have a statistically significant relationship with the cesarean section rate. Results showed that the risk-adjusted cesarean section rate increased significantly in new groups after the application of the DRG-based payment system. Conclusion: Study results provided policy implications for the reorganization of the DRG-based system should that reflects the demands of obstetricians, such as organizing a consultative body with obstetricians and establishing a reasonable fee.

• 아태비즈니스연구
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• 제14권1호
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• pp.351-364
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• 2023

Purpose - This study examines the effects of Dubai oil price and the volatility on the asymmetry of domestic gasoline price adjustment. Additionally, the study investigates the effects of "Altteul" gas-station and tax-cut policies on asymmetry. Design/methodology/approach - Firstly, the study calculates proxies for asymmetry and volatility of each window(every 3-month) by error-correction model and GARCH(1, 1) using daily domestic gas price and Dubai oil price from 2008/04/15 to 2022/12/31. Secondly, the study investigates the effects of the increasing rate of Dubai oil price, volatility, "Altteul" gas-station and tax-cut policies on asymmetry. The autoregressive distributed lag regression model is employed for estimations. Findings - The study finds that changes in the increasing rate of Dubai oil price and both types of volatility of Dubai oil price increase asymmetry. While "Altteul" gas-station and tax-cut policies decrease asymmetry. Additionally, the study fails to find that asymmetry in the Korean gasoline market in the estimation with total observations. Research implications or Originality - An increase in Dubai oil price volatility means an increase in cost uncertainty for gas-station owners. Since cost uncertainty is a kind of financial risk, the increase in volatility reinforces the asymmetry. The study provides supporting evidence for the idea.

• 대한치과의사협회지
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• 제44권10호통권449호
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• pp.658-670
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• 2006

1980년대 후반기부터 치주질환과 뇌경색(ischemic stroke)자료의 연관성을 모색하는 시도가 있어왔다. 이번 연구의 목적은 치주질환과 뇌경색 유무와의 어떤 관계가 있는지를 60세 이상의 노인을 대상으로 조사, 통계 분석하였다. 자료는 미국의 총 국민조사 격인 The Third Nation Health and Nutrition Examination Survey (NHANES III)를 이용하였다. 이번 연구에서 unadjusted logistic model 통계법을 이용하여 치아 상실수와 뇌경색 경험이 통계학적으로 유의한 수치의 상관성이 있음을 알게 되었다. 또한 나이와 흡연유무를 고려, 조정한 후 multiple logistic model 통계법으로 잔존치아가 적을수록 더욱 뇌경색에 걸릴 확률이 높음을 보였다. 그러나 두 질병에 동시에 선택된 중요한 위험인자 (risk factor)를 모두 고려, 조정 한 후에는 통계학적인 유의성을 찾지 못했다. 치은퇴축, 치주낭 깊이, 치석, 탐침시 출혈과 뇌경색 경험은 각각의 비교법에서 약간의 상관성을 보이나, 모든 통계법을 통해 일괄된 결과를 얻을 수는 없었다.

• Journal of Preventive Medicine and Public Health
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• 제57권2호
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• pp.108-119
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• 2024

Objectives: Abrupt changes in air pollution levels associated with the coronavirus disease 2019 (COVID-19) outbreak present a unique opportunity to evaluate the effects of air pollution on influenza risk, at a time when emission sources were less active and personal hygiene practices were more rigorous. Methods: This time-series study examined the relationship between influenza cases (n=22 874) and air pollutant concentrations from 2018 to 2021, comparing the timeframes before and during the COVID-19 pandemic in and around Thailand's Khon Kaen province. Poisson generalized additive modeling was employed to estimate the relative risk of hospitalization for influenza associated with air pollutant levels. Results: Before the COVID-19 outbreak, both the average daily number of influenza hospitalizations and particulate matter with an aerodynamic diameter of 2.5 ㎛ or less (PM_2.5) concentration exceeded those later observed during the pandemic (p<0.001). In single-pollutant models, a 10 ㎍/m³ increase in PM_2.5 before COVID-19 was significantly associated with increased influenza risk upon exposure to cumulative-day lags, specifically lags 0-5 and 0-6 (p<0.01). After adjustment for co-pollutants, PM_2.5 demonstrated the strongest effects at lags 0 and 4, with elevated risk found across all cumulative-day lags (0-1, 0-2, 0-3, 0-4, 0-5, and 0-6) and significantly greater risk in the winter and summer at lag 0-5 (p<0.01). However, the PM_2.5 level was not significantly associated with influenza risk during the COVID-19 outbreak. Conclusions: Lockdown measures implemented during the COVID-19 pandemic could mitigate the risk of PM_2.5-induced influenza. Effective regulatory actions in the context of COVID-19 may decrease PM_2.5 emissions and improve hygiene practices, thereby reducing influenza hospitalizations.

• 한국수자원학회논문집
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• 제56권8호
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• pp.485-496
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• 2023

최근 우리나라는 댐 운영에 있어서 다양한 가뭄 대책을 활용하여 가뭄 시 물 부족의 위험 리스크를 줄이기 위해 노력하고 있다. 이를 중심으로 다양한 연구들이 수행되었지만 가뭄 대책의 효과를 경제적인 측면에서 살펴본 연구는 현재 전무한 실정이다. 본 연구에서는 ARIMA와 Copula 기반의 장기간 모의 유입량 생성 모형과 댐별 가뭄 대책을 반영한 댐 운영 모형을 활용하여 전국의 다목적댐을 대상으로 가뭄 대책 시행에 따른 경제적 효과를 평가하였다. 경제적 편익 산정 결과 연계 운영·대체 공급과 비상공급대책의 단위 유량 당 기대 편익이 각각 1,176원과 1,139원으로 가장 높 으며, 비상 용량 활용과 용수공급조정의 편익은 956원과 875원으로 추정된다. 추가로 미래에 가뭄이 심화된다는 가정을 기반으로 가뭄 대책의 경제적 편익의 변화에 대하여 살펴본 결과 유입량 감소로 인한 가뭄 리스크의 변화는 모든 가뭄 대책의 경제적 편익을 높이는 효과를 보였다. 용수공급조정의 경제적 효과는 기존 대비 2.6% 상승하였으나, 연계 운영·대체 공급의 경제적 효과는 기존 대비 11.7% 상승하였다. 이는 가뭄의 위험도가 증가할수록 연계 운영과 대체 공급과 같은 댐 네트워크 기반의 대책이 주요한 것으로 판단된다. 본 연구는 향후 가뭄 대책의 선정과 활용에 있어서 기본자료로 활용될 것으로 기대된다.