• Communications for Statistical Applications and Methods
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• v.23 no.1
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• pp.1-20
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• 2016

Causal inference methodologies have been developed for the past decade to estimate the unconfounded effect of an exposure under several key assumptions. These assumptions include, but are not limited to, the stable unit treatment value assumption, the strong ignorability of treatment assignment assumption, and the assumption that propensity scores be bounded away from zero and one (the positivity assumption). Of these assumptions, the first two have received much attention in the literature. Yet the positivity assumption has been recently discussed in only a few papers. Propensity scores of zero or one are indicative of deterministic exposure so that causal effects cannot be defined for these subjects. Therefore, these subjects need to be removed because no comparable comparison groups can be found for such subjects. In this paper, using currently available causal inference methods, we evaluate the effect of arbitrary cutoffs in the distribution of propensity scores and the impact of those decisions on bias and efficiency. We propose a tree-based method that performs well in terms of bias reduction when the definition of positivity is based on a single confounder. This tree-based method can be easily implemented using the statistical software program, R. R code for the studies is available online.

• Journal of the Korean Data and Information Science Society
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• v.27 no.1
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• pp.91-100
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• 2016

Fuzzy matching is proposed to make propensities of two groups similar with their propensity scores and a way to select control variable to make propensity scores with a process that shows how to acquire propensity scores using logic regression analysis, is presented. With such scores, it was a method to obtain an experiment group and a control group that had similar propensity employing the Fuzzy Matching. In the study, it was proven that the two groups were the same but with a different distribution chart and standardization which made edge tolerance different and we realized that the number of chosen cases decreased when the edge tolerance score became smaller. So with the idea, we were able to determine that it is possible to merge groups using fuzzy matching without a precontrol and use them when data (big data) are used while to check the pros and cons of Fuzzy Matching were made possible.

• Survey Research
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• v.10 no.1
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• pp.169-186
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• 2009

The propensity score method is used to minimize the bias level in social survey, which comes from nonresponse. The theoretical concept and the background of the propensity score method is discussed first. The propensity score method was first applied in the epidemiology observational study. I have summarized the process of the three propensity score methods that were used to reduce estimation bias in this study. Matching by propensity score is applied to the relatively large control group. Subclassification has the advantage of using whole control group data and regression adjustment is applied to multiple covariates as well as propensity score of each unit is computable and usable. Lastly, the application procedures of propensity score method to reduce the nonresponse bias is suggested and its applicability to real situation is reviewed with the existing data.

• Journal of Family Resource Management and Policy Review
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• v.8 no.3
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• pp.47-64
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• 2004

This study compared full-time housewives' propensity for TV home shopping addiction by different socioeconomic, psychological, and purchase-related characteristics. And it identified the factors that influenced full-time housewives' TV home shopping addiction. The data were obtained from a questionnaire completed by full-time housewives (n=225) lived in Seoul and were analyzed by t-tests, ANOVA, and a multiple regression analysis. The findings of this study were as follows: First, full-time housewives' propensity for TV home shopping addiction was higher in the relatively old aged group. Those who graduated from graduate schools had lower scores in the scale of TV shopping addiction. Also, middle income group showed higher propensity for addictive buying. Second, the propensity for TV home shopping addiction was higher among those who had low self-esteem, who had higher level of empty self Also, those who had experienced material compensations as a child showed higher propensity for addictive purchase. Third, the propensity for addictive buying in TV home shopping was higher among those who had higher propensity for materialism, who took a serious view of markers or friends. Those who abuse their credit cards were more likely to have TV home shopping addiction.

• The Journal of the Korean dental association
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• v.58 no.3
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• pp.152-168
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• 2020

The propensity score matching method is a statistical method used to reduce selection bias in observational studies and to show effects similar to random allocation. There are many observational studies in dentistry research, and differences in baseline covariates between the control and case groups affect the outcome. In order to reduce the bias due to confounding variables, the propensity scores are used by equating groups based on the baseline covariates. This method is effective, especially when there are many covariates or the sample size is small. In this paper, the propensity score matching method was explained in a simple way with a dental example by using R software. This simulated data were obtained from one of retrospective study. The control group and the case group were matched according to the propensity score and compared before and after treatment. The propensity score matching method could be an alternative to compensate for the disadvantage of the observation study by reducing the bias based on the covariates with the propensity score.

• Journal of Preventive Medicine and Public Health
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• v.57 no.1
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• pp.1-7
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• 2024

Objectives: Adjusting for potential confounders is crucial for producing valuable evidence in outcome studies. Although numerous studies have been published using the Korea National Health Insurance Claim Database, no study has critically reviewed the methods used to adjust for confounders. This study aimed to review these studies and suggest methods and applications to adjust for confounders. Methods: We conducted a literature search of electronic databases, including PubMed and Embase, from January 1, 2021 to December 31, 2022. In total, 278 studies were retrieved. Eligibility criteria were published in English and outcome studies. A literature search and article screening were independently performed by 2 authors and finally, 173 of 278 studies were included. Results: Thirty-nine studies used matching at the study design stage, and 171 adjusted for confounders using regression analysis or propensity scores at the analysis stage. Of these, 125 conducted regression analyses based on the study questions. Propensity score matching was the most common method involving propensity scores. A total of 171 studies included age and/or sex as confounders. Comorbidities and healthcare utilization, including medications and procedures, were used as confounders in 146 and 82 studies, respectively. Conclusions: This is the first review to address the methods and applications used to adjust for confounders in recently published studies. Our results indicate that all studies adjusted for confounders with appropriate study designs and statistical methodologies; however, a thorough understanding and careful application of confounding variables are required to avoid erroneous results.

• Human Ecology Research
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• v.54 no.5
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• pp.529-539
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• 2016

This study confirmed shopping behavior of Korean young overseas tourists and its effect on travel evaluation. I first identified core factors of travel activity preference, travel shopping propensity, and shopping products. The effect of shopping product satisfaction on tour satisfaction and post-tour intention was then investigated. Based on travel activities, tourists were grouped, and their characteristics were compared. An online survey method was performed to obtain data of 20's-30's Korean unmarried people, while factor analysis, regression analysis, chi-square test, analysis of variance (ANOVA), and cluster analysis were applied to analyze data. The results were as follows. First, six travel activities (city life, art/shopping, cultural experience, entertainment, field experience, and friendship), three shopping propensity (novelty/uniqueness, utility, and prestige), and four product groups (fashion goods, household goods, crafts, and foods) were found by factor analyses. Second, travel activity tended to influence shopping propensity, which then influenced shopping products preference. All factors of travel activity seemed to affect the three travel shopping propensities. Third, shopping satisfaction was shown to affect tour satisfaction, and posttour behavior. Finally, four tourist groups (active, social, pleasure, and passive) differed in terms of preferred tour activities, shopping propensity, and tour behavior. Active tourists rated the highest scores and passive ones rated the lowest for most evaluations.

• Journal of Korean Academy of Nursing Administration
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• v.12 no.3
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• pp.434-443
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• 2006

Purpose: This study was to compare effects of preceptorship on nursing students' critical thinking propensity, clinical competency, and the satisfaction of clinical practice. Method: The subjects were 80 by preceptorship group and 51 by conventional method group. The data were analyzed by SPSS 12.0 program. Results: The subject's critical thinking propensity, clinical competency and satisfaction of clinical practices between the preceptorship group and the conventional method group revealed statistically significant difference. Subject's critical thinking propensity revealed significant correlations, along with the clinical competεncy and the satisfaction for clinical practice. And the clinical competency revealed statistically significant correlations with the satisfaction for clinical practice. Conclusion: Findings of this study reveals that the nursing students who had clinical practice by preceptorship showed higher scores in the critical thinking propensity, clinical competency, and the satisfaction for clinical practice than the conventional method group. Consequently, we are quite consciously encouraged to reinforce the preceptorship for realization of an effective clinical practice education for nursing students.

• Journal of the Korean earth science society
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• v.40 no.4
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• pp.436-445
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• 2019

This study presents how two types of integrated science and engineering lessons affect students' engineering problem solving skills and their perceptions of engineering. In total, 146 middle school students participated in this study. Eighty-six students participated in the Type I lesson (complete engineering design lesson with a science knowledge application) and 60 students participated in the Type II lesson (engineering design without a science knowledge application). Two main datasets, (1) students' Creative Engineering Problem Solving Propensity (CEPSP) measurement scores and (2) open-ended survey questions about students' perceptions of engineering, were collected before and after the lessons. The results of this study show that after participating in the Type I lesson, students' CEPSP scores significantly increased, whereas the CEPSP scores of the students who participated in the Type II lesson did not increase significantly. In addition, students who participated in the Type I lesson perceived engineering and the engineering integrated science lesson differently compared to the students who participated in the Type II lesson. The results of this study show that engineering integrated science, technology, engineering & mathematics (STEM) lessons should include a complete engineering design and a science knowledge application to improve students' engineering problem solving skills.

• The Korean Journal of Applied Statistics
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• v.29 no.2
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• pp.389-398
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• 2016

In this paper, we examine the financial performance of credit guarantee programs. We compared financial performance of guaranteed firms of KODIT and non-guaranteed firms. The of covariate adjusted propensity score method is used because a selection bias problem could occur if t-test or regression analysis were used. The results show that a credit guarantee program enhances the financial performance of beneficiary firms.