• 응용통계연구
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• 제29권5호
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• pp.773-786
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• 2016

분위수 회귀는 반응변수의 조건부 분위수 함수를 추정함으로써 반응변수와 예측변수의 관계에 대한 포괄적인 정보를 제공한다. 그러나 여러 개의 분위수 함수를 개별적으로 추정하게 되면 이들이 서로 교차할 가능성이 있으며, 이러한 분위수 함수의 교차(quantile crossing) 현상 분위수의 이론적 기본 특성에 위배된다. 본 논문에서는 다중 비교차 분위수 함수의 추정의 대표적인 방법들의 특성을 적합식과 계산 알고리즘의 측면에서 살펴보고, 모의실험과 실제 자료 분석을 통해 그 성능을 비교하였다.

• Communications for Statistical Applications and Methods
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• 제19권2호
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• pp.293-301
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• 2012

Quantile regression proposed by Koenker and Bassett (1978) is a statistical technique that estimates conditional quantiles. The advantage of using quantile regression is the robustness in response to large outliers compared to ordinary least squares(OLS) regression. A regression tree approach has been applied to OLS problems to fit flexible models. Loh (2002) proposed the GUIDE algorithm that has a negligible selection bias and relatively low computational cost. Quantile regression can be regarded as an analogue of OLS, therefore it can also be applied to GUIDE regression tree method. Chaudhuri and Loh (2002) proposed a nonparametric quantile regression method that blends key features of piecewise polynomial quantile regression and tree-structured regression based on adaptive recursive partitioning. Lee and Lee (2006) investigated wage determinants in the Korean labor market using the Korean Labor and Income Panel Study(KLIPS). Following Lee and Lee, we fit three kinds of quantile regression tree models to KLIPS data with respect to the quantiles, 0.05, 0.2, 0.5, 0.8, and 0.95. Among the three models, multiple linear piecewise quantile regression model forms the shortest tree structure, while the piecewise constant quantile regression model has a deeper tree structure with more terminal nodes in general. Age, gender, marriage status, and education seem to be the determinants of the wage level throughout the quantiles; in addition, education experience appears as the important determinant of the wage level in the highly paid group.

• Journal of Preventive Medicine and Public Health
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• 제54권2호
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• pp.145-152
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• 2021

Objectives: This study aimed to identify regional differences in the high-risk drinking rate among yearly alcohol users in Korea and to identify relevant regional factors for each quintile using quantile regression. Methods: Data from 227 counties surveyed by the 2017 Korean Community Health Survey (KCHS) were analyzed. The analysis dataset included secondary data extracted from the Korean Statistical Information Service and data from the KCHS. To identify regional factors related to the high-risk drinking rate among yearly alcohol users, quantile regression was conducted by dividing the data into 10%, 30%, 50%, 70%, and 90% quantiles, and multiple linear regression was also performed. Results: The current smoking rate, perceived stress rate, crude divorce rate, and financial independence rate, as well as one's social network, were related to the high-risk drinking rate among yearly alcohol users. The quantile regression revealed that the perceived stress rate was related to all quantiles except for the 90% quantile, and the financial independence rate was related to the 50% to 90% quantiles. The crude divorce rate was related to the high-risk drinking rate among yearly alcohol users in all quantiles. Conclusions: The findings of this study suggest that local health programs for high-risk drinking are needed in areas with high local stress and high crude divorce rates.

• Journal of the Korean Data and Information Science Society
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• 제28권3호
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• pp.533-545
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• 2017

분위수 회귀모형은 반응변수의 조건부 분포에 대하여 포괄적이고 유용한 통계적 정보를 제공한다. 그러나 많은 실제 자료는 설명변수와 반응변수가 비선형의 관계를 갖고 있어 전통적인 선형 분위수 회귀모형은 왜곡되고 잘못된 결과를 초래할 수 있다. 또한 자료의 복잡성이 증가하여 반응변수가 여러개인 다변량 자료의 분석에 대한 보다 정확한 예측과 더불어 풍부한 해석에 대한 요구가 증가하고 있다. 이러한 이유로 본 연구에서는 다변량 분위수 회귀나무 모형을 제안하였다. 본 연구에서는 기존의 다변량 회귀나무 모형의 분할변수 선택 알고리즘의 문제점을 지적하고 향상된 분할변수 선택 알고리즘을 제안하였다. 제안한 알고리즘은 합리적인 계산시간으로 적용 가능하며 분할변수 선택에서 편향 발생의 문제를 갖지 않는 동시에 기존 방법보다 더 정확하게 분할변수를 선택할 수 있있다. 본 연구에서는 모의실험과 실증 예제를 통해 제안한 방법의 우수한 성능과 유용성을 확인하였다.

• 한국수자원학회논문집
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• 제42권6호
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• pp.465-480
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• 2009

본 연구에서는 다중회귀분석을 이용하여 산악효과를 야기하는 지형인자와 강수와의 관계를 파악하였다. 섬 전체가 산악지형인 제주도의 연평균강수량과 지수홍수법으로 산출한 확률강우량을 강수자료로 사용하여 산악효과를 야기하는 지형인자로 선정한 고도, 위 경도와 회귀모형을 구성하였다. 회귀분석 결과 연평균강수량과 고도와의 선형관계가 확률강우량에서도 동일하게 나타났으며, 고도이외에 위도, 경도를 각각 추가인자로 고려할 경우 강우량과 더욱 강한 상관성을 보였다. 또한, 고도와 위도, 경도를 모두 고려한 회귀모형을 이용한 지형공간분석 결과 제주도의 실제 강수특성과 마찬가지로 남동부로 편중된 강수형태를 보여 모형의 적합성을 증명하였다. 그러나 지속시간 및 재현기간과 무관하게 높은 고도에서 회귀식의 유효성이 감소하므로, 높은 고도에서의 추가적인 산악효과인자의 강수량에 대한 영향이 존재될 것으로 판단되므로 추후 연구가 필요하다.

• Annals of Occupational and Environmental Medicine
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• 제35권
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• pp.23.1-23.14
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• 2023

Background: Exposure to heavy metals is a public health concern worldwide. Previous studies on the association between heavy metal exposure and neurobehavioral functions in children have focused on single exposures and clinical manifestations. However, the present study evaluated the effects of heavy metal complex exposure on subclinical neurobehavioral function using a Korean Computerized Neurobehavior Test (KCNT). Methods: Urinary mercury, lead, cadmium analyses as well as symbol digit substitution (SDS) and choice reaction time (CRT) tests of the KCNT were conducted in children aged between 10 and 12 years. Reaction time and urinary heavy metal levels were analyzed using partial correlation, linear regression, Bayesian kernel machine regression (BKMR), the weighted quantile sum (WQS) regression and quantile G-computation analysis. Results: Participants of 203 SDS tests and 198 CRT tests were analyzed, excluding poor cooperation and inappropriate urine sample. Partial correlation analysis revealed no association between neurobehavioral function and exposure to individual heavy metals. The result of multiple linear regression shows significant positive association between urinary lead, mercury, and CRT. BMKR, WQS regression and quantile G-computation analysis showed a statistically significant positive association between complex urinary heavy metal concentrations, especially lead and mercury, and reaction time. Conclusions: Assuming complex exposures, urinary heavy metal concentrations showed a statistically significant positive association with CRT. These results suggest that heavy metal complex exposure during childhood should be evaluated and managed strictly.

• 지역사회간호학회지
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• 제24권3호
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• pp.273-281
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• 2013

Purpose: The purpose of this study was to determine gender differences in effects of self-efficacy, exercise benefits and barriers, and demographic factors on the physical activity. Methods: Seventy sedentary office workers, 35 male and 35 female, from a major airline company, completed a questionnaire from March 28 to April 5, 2012. Steps and body mass indices were measured using a CW-700/701 (Yamax) pedometer and Inbody 720 (Biospace), respectively. Data were analyzed using t-test, $x^2$-test, multiple linear regression, and simultaneous quantile regression. Results: For male workers, exercise self-efficacy had a significant effect on physical activity, but only when respondents were at 10%(3,431 steps/day, p=.018) and 25%(4,652 steps/day, p=.044) of the physical activity distribution. For female workers, marital status was significantly related to physical activity, but only when respondents were at 10% (3,537 steps/day, p=.013) and 25%(3,862 steps/day, p=.014) of the physical activity distribution. Conclusion: Quantile regression highlights the heterogeneous effect of physical activity determinants among office workers. Therefore intervention strategies for increasing physical activity should be tailed to genders as well as physical activity levels.

• Human Ecology Research
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• 제60권2호
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• pp.289-302
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• 2022

This study examined the effect of private educational expenditure on adolescent depression and somatic symptoms. The sample comprised 2,589 first-grade middle-school students who completed the 2018 Korea Children and Youth Panel Survey. Data were analyzed using ANOVA (the generalized linear model), multiple regression, and quantile regression analysis. The principal results were as follows. First, 15.15% of adolescents reported depression symptoms, and 15.57% reported somatic symptoms. Second, levels of depression were significantly different among classes with a different level of private educational expenditure. Third, depression level was significantly negatively associated with private educational expenditure, in that the higher the private educational expenditure, the lower the depression level. Fourth, the effect of private educational expenditure on adolescent depression was significant at the 70~90th quantile regression, suggesting that private educational expenditure was associated with a higher level of depression symptoms. The results indicate that private education was viewed as a consumption commodity rather than a complementary educational practice or investment in human capital. Private education as a commodity might induce the highly developed and costly private education market. In turn, there is an increased financial burden for education at one end of the social-economic continuum and depression caused by relative deprivation at the other end.

• Journal of Korea Trade
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• 제26권1호
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• pp.113-125
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• 2022

Purpose - The primary purpose of this study is to verify whether the target set out by the International Maritime Organization (IMO) for reducing carbon emissions from ships can be achieved by quantitatively analyzing the trends in technological advances of fuel oil consumption in the container shipping market. To achieve this purpose, several scenarios are designed considering various options such as eco-friendly fuels, low-speed operation, and the growth in ship size. Design/methodology - The vessel size and speed used in prior studies are utilized to estimate the fuel oil consumption of container ships and the pace of technological progress and Energy Efficiency Design Index (EEDI) regulations are added. A database of 5,260 container ships, as of 2019, is used for multiple linear regression and quantile regression analyses. Findings - The fuel oil consumption of vessels is predominantly affected by their speed, followed by their size, and the annual technological progress is estimated to be 0.57%. As the quantile increases, the influence of ship size and pace of technological progress increases, while the influence of speed and coefficient of EEDI variables decreases. Originality/value - The conservative estimation of carbon emission drawn by a quantitative analysis of the technological progress concerning the fuel efficiency of container vessels shows that it is not possible to achieve IMO targets. Therefore, innovative efforts beyond the current scope of technological progress are required.

• Journal of the Korean Data and Information Science Society
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• 제28권6호
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• pp.1457-1469
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• 2017

일반계 고등학생의 사교육비 지출은 대학입시와 맞물려 최근 더욱 증가하고 있는 동시에 가구소득 수준, 지역 등에 따라 양극화되고 있다. 기존의 사교육비 연구는 주로 다중회귀모형을 토대로 최소자승법을 이용하였으나 자료가 최소자승법의 기본가정인 정규성과 등분산성을 만족하지 않으면 분석결과의 신뢰성에 대한 문제가 발생된다. 본 연구는 2015년도 사교육실태조사자료에 대하여 정규성과 등분산성이 성립되지 않음을 확인하고 이를 통제할 수 있는 베이지안 분위회귀모형을 적합한 후 깁스 샘플링 방법을 이용하여 사교육비 지출규모 수준 (분위수)에 따라 영향요인들을 분석하였다. 분석결과 학생의 성별, 부모의 나이, 방과후 학교 참여시간과 비용은 사교육비 지출규모에 의미있는 영향을 주지 못하였다. 가구소득은 사교육비 지출규모의 모든 수준에서 동일하게 영향을 주는 요인으로 파악되었다. 그 외, 거주지역, 총사교육시간, 학생의 성적, 부모의 교육정도, 가구의 경제활동주체, 방과후 학교 참여여부, EBS 교재비용은 사교육비 지출 규모의 수준에 따라 다르게 영향을 주었다.