• Title/Summary/Keyword: Bivariate Measures

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Hydrological homogeneous region delineation for bivariate frequency analysis of extreme rainfalls in Korea (다변량 L-moment를 이용한 이변량 강우빈도해석에서 수문학적 동질지역 선정)

  • Shin, Ju-Young;Jeong, Changsam;Joo, Kyungwon;Heo, Jun-Haeng
    • Journal of Korea Water Resources Association
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    • v.51 no.1
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    • pp.49-60
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    • 2018
  • The multivariate regional frequency analysis has many advantages such as an adaption of regional parameters and consideration of a correlated structure of the data. The multivariate regional frequency analysis can provide the broader and more detailed information for the hydrological variables. The multivariate regional frequency analysis has not been attempted to model hydrological variables in South Korea yet. Therefore, it is required to investigate the applicability of the multivariate regional frequency analysis in the modeling of the hydrological variables. The current study investigated the applicability of the homogeneous region delineation and their characteristics in bivariate regional frequency analysis of annual maximum rainfall depth-duration data. The K-medoid method was employed as a clustering method. The discordancy and heterogeneous measures were used to assess the appropriateness of the delineation results. According to the results of the clustering analysis, the employed stations could be grouped into five regions. All stations at three of the five regions led to acceptable values of discordancy measures than the threshold. The stations where have short record length led to the large discordancy measures. All grouped regions were identified as a homogeneous region based on heterogeneous measure estimates. It was observed that there are strong cross-correlations among the stations in the same region.

Firework plot for evaluating the impact of outliers in statistical inference (통계적 추론에서 특이점의 영향을 평가하기 위한 탐색적 자료분석 그림도구로서의 불꽃그림)

  • Moon, Sungho
    • The Korean Journal of Applied Statistics
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    • v.31 no.1
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    • pp.155-165
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    • 2018
  • Outliers and influential observations often distort many numerical measures for data analysis. Jang and Anderson-Cook (Quality and Reliability Engineering International, 30, 1409-1425, 2014) proposed a graphical firework plot method for exploratory analysis purpose to provide a possible visualization of the trace of the impact of the possible outlying and influential observations on the univariate/bivariate data analysis and regression. They developed 3-D plot as well as pairwise plot for the appropriate measures of interest. We use firework plots as a graphical exploratory data analysis tool to detect outliers and evaluate the impact of outliers in statistical inference.

Firework plot as a graphical exploratory data analysis tool for evaluating the impact of outliers in skewness and kurtosis of univariate data (일변량 자료의 왜도와 첨도에서 특이점의 영향을 평가하기 위한 탐색적 자료분석 그림도구로서의 불꽃그림)

  • Moon, Sungho
    • The Korean Journal of Applied Statistics
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    • v.29 no.2
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    • pp.355-368
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    • 2016
  • Outliers and influential data points distort many data analysis measures. Jang and Anderson-Cook (2014) proposed a graphical method called a rework plot for exploratory analysis purpose so that there could be a possible visualization of the trace of the impact of the possible outlying and/or influential data points on the univariate/bivariate data analysis and regression. They developed 3-D plot as well as pairwise plot for the appropriate measures of interest. This paper further extends their approach to identify its strength. We can use rework plots as a graphical exploratory data analysis tool to evaluate the impact of outliers in skewness and kurtosis of univariate data.

Relationship between the Difficulty of Securing Farmland and Demand for Farmland Information (농지확보의 어려움과 농지정보 수요간의 관계 분석)

  • Yi, Hyang-Mi
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.21 no.11
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    • pp.264-272
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    • 2020
  • In this study, for the people who turned or returned to farming (the "Returnees"), information provision measures were sought, focusing on "farmland," for their difficulties in the settlement phase and finding a way for their new agricultural companies to settle in the farming business stably. For this purpose, this study considered endogeneity using a bivariate probit model. According to the results of the study, first, there is a strong positive correlation between the difficulty of securing farmland and the demand for providing farmland information in the settlement phase. Therefore, to ensure the stable settlement of the Returnees, it is necessary to actively respond to their demand through the provision of farmland information. Second, for young returnees, the probability of encountering difficulties in securing farmland is high during the settlement phase. Third, if the young returnees returned to farming after seeing the possibility of agricultural development, the possibility of securing farmland in the settlement stage decreases, and although there was no statistical significance, the demand for farmland information also decreases. Fourth, it was found that if the returnees intend to expand the scale of farming in the future, it is difficult to secure farmland in the settlement phase, and the demand for farmland information also increases.

Spatial Data Analysis for the U.S. Regional Income Convergence,1969-1999: A Critical Appraisal of $\beta$-convergence (미국 소득분포의 지역적 수렴에 대한 공간자료 분석(1969∼1999년) - 베타-수렴에 대한 비판적 검토 -)

  • Sang-Il Lee
    • Journal of the Korean Geographical Society
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    • v.39 no.2
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    • pp.212-228
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    • 2004
  • This paper is concerned with an important aspect of regional income convergence, ${\beta}$-convergence, which refers to the negative relationship between initial income levels and income growth rates of regions over a period of time. The common research framework on ${\beta}$-convergence which is based on OLS regression models has two drawbacks. First, it ignores spatially autocorrelated residuals. Second, it does not provide any way of exploring spatial heterogeneity across regions in terms of ${\beta}$-convergence. Given that empirical studies on ${\beta}$-convergence need to be edified by spatial data analysis, this paper aims to: (1) provide a critical review of empirical studies on ${\beta}$-convergence from a spatial perspective; (2) investigate spatio-temporal income dynamics across the U.S. labor market areas for the last 30 years (1969-1999) by fitting spatial regression models and applying bivariate ESDA techniques. The major findings are as follows. First, the hypothesis of ${\beta}$-convergence was only partially evidenced, and the trend substantively varied across sub-periods. Second, a SAR model indicated that ${\beta}$-coefficient for the entire period was not significant at the 99% confidence level, which may lead to a conclusion that there is no statistical evidence of regional income convergence in the US over the last three decades. Third, the results from bivariate ESDA techniques and a GWR model report that there was a substantive level of spatial heterogeneity in the catch-up process, and suggested possible spatial regimes. It was also observed that the sub-periods showed a substantial level of spatio-temporal heterogeneity in ${\beta}$-convergence: the catch-up scenario in a spatial sense was least pronounced during the 1980s.

Assessment of hydrological drought risk in the southern region in 2022: based on bivariate regional drought frequency analysis (2022년 남부지역 수문학적 가뭄위험도 평가: 수문학적 이변량 가뭄 지역빈도해석 중심으로)

  • Kim, Yun-Sung;Jung, Min-Kyu;Kim, Tae-Woong;Jeong, Seung-Myeong;Kwon, Hyun-Han
    • Journal of Korea Water Resources Association
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    • v.56 no.2
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    • pp.151-163
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    • 2023
  • This study explored the 2022 drought over the Nakdong River watershed. Here, we developed a bivariate regional frequency analysis method to evaluate the risk of hydrological drought. Currently, natural streamflow data are generally limited to accurately estimating the drought frequency. Under this circumstance, the existing at site frequency analysis can be problematic in estimating the drought risk. On the other hand, a regional frequency analysis could provide a more reliable estimation of the joint return periods of drought variables by pooling available streamflow data over the entire watershed. More specifically, the Copula-based regional frequency analysis model was proposed to effectively take into account the tail dependencies between drought variables. The results confirmed that the regional frequency analysis model showed better performance in model fit by comparing the goodness-of-fit measures with the at-site frequency analysis model. We find that the estimated joint return period of the 2022 drought in the Nakdong River basin is about eight years. In the case of the Nam river Dam, the joint return period was approximately 20 years, which can be regarded as a relatively severe drought over the last three decades.

Smoking Behavior and Predictors of Smoking Initiation in Childhood and Early Adolescence (학령기 및 청소년 초기 흡연행태와 흡연시작에 영향을 주는 요인)

  • Park, Sun-Hee
    • Journal of Korean Academy of Nursing
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    • v.39 no.3
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    • pp.376-385
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    • 2009
  • Purpose: The purposes of this study were(a) to identify smoking behavior by following a cohort representative of the population of 4th grade elementary schoolers in South Korea over a four-year period(2004-2007), and(b) to explore predictors of smoking initiation among non-smokers in Wave 1. Methods: Secondary data, the Korea Youth Panel Study, was analyzed in this study. First, frequencies or percentages were calculated to identify smoking behavior(i.e., smoking initiation, smoking intensity, and smoking duration). Second, binary logistic regression analysis was performed to examine significant factors related to smoking initiation. Results: Smoking initiation and daily smoking were more pronounced when the participants entered middle school. In bivariate analysis, statistically significant predictors of smoking initiation were loneliness at school, self-control, delinquent behavior, depressive symptoms, and stress. However, after controlling for other factors, only a high level of risk-taking tendency and a greater number of delinquent behaviors remained statistically significant. Conclusion: Based on greater involvement in smoking among first-year middle schoolers, smoking prevention strategies should be provided to elementary schoolers rather than middle schoolers. A risk-taking tendency and delinquent behaviors should be considered as proxy measures to detect the high-risk group for smoking initiation.

Nutritional Support, Gastric Residual Volume and Nutritional Status during Enteral Nutrition in Intensive Care Unit Patients (중환자실 경장영양 환자의 영양지원, 위 잔여량 및 영양상태)

  • Lee, Minju;Kang, Jiyeon
    • Korean Journal of Adult Nursing
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    • v.26 no.6
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    • pp.621-629
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    • 2014
  • Purpose: The purpose of this study was to investigate the nutritional support, gastric residual volume, and nutritional status of the intensive care unit (ICU) patients on enteral feeding. Methods: A descriptive longitudinal design was used to collect 5 day data on enteral nutrition of 52 ICU patients in an university hospital. Nutritional support was calculated with actual caloric intake compared to individual caloric requirement. Residual volumes were measured prior to routine feedings, and the serum albumin levels and the total lymphocyte counts were checked to evaluate nutritional status. The data were analyzed using one group repeated measures ANOVA, paired t-test, and Spearman's bivariate correlation analysis. Results: The subjects received their first enteral feeding on the $5.75^{th}$ day of ICU admission. The mean nutritional support rate was 49.1% of the requirement, however prescription rate and support rate were increased as time goes by. Gastric residual volumes were less than 10 cc in 95% cases. A significant negative correlation was found between nutritional support and nutritional status. Conclusion: The nutritional support for ICU patient was low compared to the requirement, and their nutritional status was worse than at the time of ICU admission. Further studies are necessary to develop nursing interventions for improving nutritional support for ICU patients.

The Relationships Between Perception of Supervisors' Autonomy Support, Volunteer Motivation and Persistence Intentions Among Collegiate Volunteers (대학생 자원봉사자가 지각한 슈퍼바이저의 자율성지지, 자원봉사동기 및 지속의도 간의 관계 분석)

  • Hong, Yeon-Sook
    • Korean Journal of Social Welfare
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    • v.62 no.4
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    • pp.103-128
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    • 2010
  • This study applied self-determination theory to investigate the relationships between volunteers' perception of supervisors' autonomy support, volunteering motivation, and persistence intentions among collegiate students. Collegiate volunteers(n=515) involved in volunteer activities completed measures of supervisors' autonomy support, 5 forms regulation, and persistence intentions. Bivariate correlations indicated that volunteer motivation demonstrated an ordered pattern of relationships, such that adjunct points along the regulatory continuum would be more positively associated with on another than distal points. Analyses using structural equation modeling revealed that supervisors' autonomy support was positively related to more autonomous motivation(intrinsic motivation and identified regulation), while was natively associated with amotivation. Amotivation was negatively related with persistence intentions, and more autonomous motivations(intrinsic and identified) predicted grater intentions to continue with volunteer activity for next 6 months. The findings are discussed in light of the self-determination theory.

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A Study of the Influence of Choice of Record Fields on Retrieval Performance in the Bibliographic Database (서지 데이터베이스에서의 레코드 필드 선택이 검색 성능에 미치는 영향에 관한 연구)

  • Heesop Kim
    • Journal of the Korean Society for Library and Information Science
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    • v.35 no.4
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    • pp.97-122
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    • 2001
  • This empirical study investigated the effect of choice of record field(s) upon which to search on retrieval performance for a large operational bibliographic database. The query terms used in the study were identified algorithmically from each target set in four different ways: (1) controlled terms derived from index term frequency weights, (2) uncontrolled terms derived from index term frequency weights. (3) controlled terms derived from inverse document frequency weights, and (4) uncontrolled terms based on universe document frequency weights. Su potable choices of record field were recognised. Using INSPEC terminology, these were the fields: (1) Abstract. (2) 'Anywhere'(i.e., ail fields). (3) Descriptors. (4) Identifiers, (5) 'Subject'(i.e., 'Descriptors' plus Identifiers'). and (6) Title. The study was undertaken in an operational web-based IR environment using the INSPEC bibliographic database. The retrieval performances were evaluated using D measure (bivariate in Recall and Precision). The main findings were that: (1) there exist significant differences in search performance arising from choice of field, using 'mean performance measure' as the criterion statistic; (2) the rankings of field-choices for each of these performance measures is sensitive to the choice of query : and (3) the optimal choice of field for the D-measure is Title.

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