• Proceedings of the Korean Statistical Society Conference
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• 2003.10a
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• pp.263-268
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• 2003

Breiman, Friedman, Olshen and Stone(1984)의 전체탐색법에 의한 회귀나무는 상대적으로 많은 분리가 가능한 변수로 분리기준이 정해지는 편의 현상을 갖고 있다. 본 연구에서는 이런 문제점을 해결할 수 있는 알고리즘을 제안하여 변수선택편의가 없는 회귀나무를 만들고자 한다. 제안하는 알고리즘은 노드의 분리변수를 선택하는 단계와 그 선택된 변수에 의해 이진분리를 위한 분리점을 찾는 단계로 구성되어 있다. 예측변수 중에서 목표변수와 가장 밀접하게 연관된 예측변수는 예측변수의 자료의 종류에 따라 스피어만의 순위상관계수에 의한 검정 혹은 크루스칼-왈리스의 통계량에 의한 검정을 수행하여 가장 통계적으로 유의한 변수로 선택하였고, 선택된 변수에만 Breiman et al.(1984)의 전체선택법을 적용하여 분리점을 결정하였다. 모의실험을 통해 변수선택편의, 변수선택력 , 그리고 평균제곱오차 측면에서 Breiman et al. (1984)의 CART(Classification and Regression Trees)와 제안한 알고리즘을 서로 비교하였다. 또한, 두 알고리즘을 실제 자료에 적용하여 효율을 서로 비교하였다.

• The Korean Journal of Applied Statistics
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• v.17 no.3
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• pp.459-473
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• 2004

It has well known that an exhaustive search algorithm suggested by Breiman et. a1.(1984) has a trend to select the variable having relatively many possible splits as an splitting rule. We propose an algorithm to overcome this variable selection bias problem and then construct unbiased regression trees based on the algorithm. The proposed algorithm runs two steps of selecting a split variable and determining a split rule for binary split based on the split variable. Simulation studies were performed to compare the proposed algorithm with Breiman et a1.(1984)'s CART(Classification and Regression Tree) in terms of degree of variable selection bias, variable selection power, and MSE(Mean Squared Error). Also, we illustrate the proposed algorithm with real data sets.

• The Korean Journal of Applied Statistics
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• v.16 no.1
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• pp.151-167
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• 2003

Although there exist numerous measures of association, most of them are lacking in generality in that they do not intend to measure the association between heterogeneous type of random variables. On the other hand, many statistical analyzes dealing with complex data sets require a very sophisticate measure of association. In this note, the p-value of independence tests is utilized to obtain a measure of association. The proposed measure of association have some consistency in measuring association between various types of random variables.

• The Korean Journal of Applied Statistics
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• v.34 no.4
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• pp.523-536
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• 2021

Although there exist numerous measures of association, most of them are lacking in generality in that they do not intend to measure the association between heterogeneous type of random variables. On the other hand, many statistical analyzes dealing with complex data sets require a very sophisticate measure of association. In this note, the p-value of independence tests is utilized to obtain a measure of association. The proposed measure of association have some consistency in measuring association between various types of random variables.

• Journal of KIISE:Software and Applications
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• v.41 no.8
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• pp.598-604
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• 2014

In this paper, we develop stepwise regression data envelopment model to select important variables. We formulate null hypothesis to understand the importance of each variable and use Kruskal-Wallis test for this purpose. If the Kruskal-Wallis test does reject the null hypothesis this will imply there is significant fluctuation in the efficiency score relative to base model. And therefore we have to further check the pair of variables that causes the fluctuation in order to determine its importance using Conover-Inman test. The proposed models helps understand the extent of misclassification decision making units as efficient/inefficient when variables are retained or discarded alongside provides useful managerial prescription to make improvement strategies.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.28 no.2
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• pp.53-62
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• 2020

This study is to evaluate the accuracy of the meteorological information provided for the aircraft operating at low altitude. At first, it is necessary to identify crucial elements of weather information closely related to flight safety during low altitude flights. The study conducted a survey of pilots of low altitude aircraft, divided into pre-flight and in-flight phases, and reached an opinion that wind direction, wind speed, cloud coverage and ceiling and visibility are important items. Related to these items, we compared and calculated the accuracy of TAFs and METARs from Taean Airfield, Seosan Airport and Gunsan Airport because of their high number of domestic low-altitude flights. Accuracy analysis evaluated the accuracy of two numerical variables, Mean Absolute Error(MAE) and Root Mean Square Error(RMSE), and the cloud coverage which is categorical variable was calculated and compared by accuracy. For numeric variables, one-way ANOVA, which is a parameter-test, was approached to identify differences between actual forecast values and observations based on absolute errors for each item derived from the results of MAE and RMSE accuracy analyses. To determine the satisfaction of both normality assumptions and equivalence variability assumptions, the Shapiro-Wilk test was performed to verify that they do not have a normality distribution for numerical variables, and for the non-parametric test, Kruscal-Wallis test was conducted to determine whether or not they are satisfied.

• The Journal of the Korea Contents Association
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• v.20 no.7
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• pp.503-515
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• 2020

This study was conducted to find out the psychosocial-demographic factors affecting the ambivalent sexism and attitudes toward homosexuality of school health teachers. The data were collected from December 1^st to 31^st, 2019 by administering a structured online questionnaire for 138 school health teachers in S city. The data were analyzed via SPSS/WIN (25.0) to run Kruskal-Wallis 𝑥² test, Mann-Whitney U test, Spearman's rank correlation, and Stepwise multiple regression. The results showed that the influential factors on the hostile sexism include authoritarian personality, age, extrinsic religious orientation, and education. Compared to this, the benevolent sexism had the influential factors of authoritarian personality, age, and education. The influential factors to the attitudes toward homosexuality found to include authoritarian personality, whether or not have a religion, and intrinsic/extrinsic religious orientation. School health teachers affect the educational experiences of students of their gender stereotyping and prejudice in the school environments. Therefore, it is needed to establish and provide training programs for school health teachers so that they can have reflections on their gender perspectives themselves, which may lead to true educational changes based on gender equality.

• Korean Business Review
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• v.6
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• pp.201-228
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• 1993

The objective of this research is to investigate the attetudes of religious groups(christian, buddhist, atheist) towards corporate social expenditures. Methodology was a questionnair survey. The data analysis was done by the Kruscal Wallis test and Wilcoxon signed ranks test. The results of this rssearch is that the difference of attitudes between christian group and other groups and between religious groups and atheist group on the social expenditures did not turn out to be statistically significant. The implication of this results is that the variables of religious groups can be ignored when we are going to study on the attitudes of values for the Korean people.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.2
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• pp.252-259
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• 2014

The obligation of web accessibility in public center, education center, medical center and rehabilitation center started from 2009 has plan to adapt it to a corporation and culture and art until 2015 by stages. This study analysed in the aspect of statistics how well the domestic broadcasting system follows web accessibility which was evaluated by six automatic checking guidelines provided in KWA-H 4.3 automatic evaluation device. With Kruskal-Wallis' test result of nonparametric analysis, an item of basic language statement seemed to be highly followed(p=0.041) with broadcasting system> internet newspaper> the daily press> sports newspaper in order. An item of label offering was followed(p=0.015) with sports newspaper> broadcasting system> the daily press> internet newspaper in order.

• Journal of the Korea Convergence Society
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• v.13 no.3
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• pp.91-103
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• 2022

This study surveyed 101 occupational therapists who were performing occupational therapy before and after the COVID-19 outbreak to compare their perceptions and performance of hand washing, use of personal protective equipment, and infection control of surrounding environment. Mann-Whitney U test, Kruskal wallis H test, Wilcoxon signed-rank test, Pearson's correlation coefficient were used analyzed. As a result, it was confirmed that they received better infection control education after the outbreak compared to before the outbreak of COVID-19, and their experience with infectious diseases was lower. In addition, it was found that the perception and performance of infection control in hand washing, personal protective equipment, and surrounding environment cleaning were improved after the outbreak compared to before the outbreak of COVID-19. However, to this day, hand washing for more than 40 seconds in running water recommended by the Korea Centers for Disease Control and Prevention, cleaning the treatment room, and disinfection of treatment tools are still in need of improvement. Through this study, infection control education should be repeated regularly to minimize the occurrence of infectious diseases, and It will be a basic data that can be used in infection control education and follow-up studies for occupational therapists in the future.