• The Korean Journal of Applied Statistics
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• v.36 no.6
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• pp.547-559
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• 2023

Proper handling of nonresponse in sample survey improves the accuracy of the parameter estimation. Various studies have been conducted to properly handle MAR (missing at random) nonresponse or MCAR (missing completely at random) nonresponse. When nonresponse occurs, the PSA (propensity score adjusted) estimator is commonly used as a mean estimator. The PSA estimator is known to be unbiased when known sample weights and properly estimated response probabilities are used. However, for MNAR (missing not at random) nonresponse, which is affected by the value of the study variable, since it is very difficult to obtain accurate response probabilities, bias may occur in the PSA estimator. Chung and Shin (2017, 2022) proposed a post-stratification method to improve the accuracy of mean estimation when MNAR nonresponse occurs under a non-informative sample design. In this study, we propose a double post-stratification method to improve the accuracy of the naive PSA estimator for MNAR nonresponse under an informative sample design. In addition, we perform simulation studies to confirm the superiority of the proposed method.

• Journal of Science Education
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• v.36 no.1
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• pp.14-21
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• 2012

We investigated the relationship of brain dominance with mathematics and science achievement. The participants were 131 middle school students (male: 74, female: 57). It was found that the above average group in mathematics and science achievement had the highest frequency with left lower brain (LLB) (mathematics: 33.8%, science: 35.0%), whereas the below average group in mathematics and science achievement had the highest frequency with right lower brain (RLB) (mathematics: 38.7%, science: 36.1%). The LLB score showed a significant difference between the above average group and the below average group in science (p<.05). In the correlational analysis, the LLB scores had the highest correlation coefficients (mathematics: r=.28, science: r=.26). The LUB scores had the second highest correlation coefficients (mathematics: r=.18, science: r=.24). These results suggest that LLB and LUB are related to mathematics and science achievement. Therefore, we insist that the assessment of mathematics and science achievement should consider brain dominance.

• Science of Emotion and Sensibility
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• v.14 no.2
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• pp.245-256
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• 2011

This study consists of two sections to figure out the relationship between autistic features and empathizing-systemizing traits. For the first section, the research involved 355 university students to measure their EQ, SQ-R and AQ. As a result, it is found that AQ was negatively correlated to EQ, and D score(relative difference between EQ and SQ-R of the individuals), but it was not significantly related to SQ-R. It means that the subject has high AQ if he has relatively lower EQ than SQ-R. For the second section, the subjects were divided into two groups based on their AQ score; the subjects who had a tendency of autism and the subjects who did not. The test measured how these two groups were different in terms of facial expressions' recognition according to the tendency of autism, facial expression presenting areas(whole face, eyes-alone, mouth-alone) and different types of emotions(basic and complex emotions). As a result, the subjects who had a tendency of autism were lower at judging facial expressions than the subjects who did not. Also, the results showed that the subjects judged better on the condition of basic emotions more than complex emotions, the whole face more than eyes-alone and mouth-alone. Especially, for the eyes-alone condition, the subjects who had a tendency of autism were lower at judging facial expressions than the subjects who did not. This study suggests that empathizing traits and facial expressions' recognition are related to the tendency of autism.

• The Korean Journal of Applied Statistics
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• v.36 no.5
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• pp.415-445
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• 2023

Oftentimes, the time dependent treatment covariate and the time dependent confounders exist in observation studies. It is an important problem to correctly adjust for the time dependent confounders in the propensity score analysis. Recently, In the survival data, Hade et al. (2020) used a propensity score matching method to correctly estimate the treatment delay effect when the time dependent confounder affects time to the treatment time, where the treatment delay effects is defined to the delay in treatment reception. In this paper, we proposed the Cox model based marginal structural model (Cox-MSM) framework to estimate the treatment delay effect and conducted extensive simulation studies to compare our proposed Cox-MSM with the propensity score matching method proposed by Hade et al. (2020). Our simulation results showed that the Cox-MSM leads to more exact estimate for the treatment delay effect compared with two sequential matching schemes based on propensity scores. Example from study in treatment discontinuation in conjunction with simulated data illustrates the practical advantages of the proposed Cox-MSM.

• Proceedings of the Korea Contents Association Conference
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• 2018.05a
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• pp.383-384
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• 2018

최근 주말의 개념이 확장되고 일상보다 여유를 우위를 두는 사람들이 많아짐에 따라 여행 산업이 발전하고 있다. 본 논문에서는 사용자 성향을 기반으로 하이브리드 협업 필터링을 이용한 여행지 추천 기법을 제안한다. 사용자별 여행지 선호도를 생성하고 사용자 기반 협업 필터링을 통해 후보 여행지를 생성하고 아이템 기반 협업 필터링을 수행하여 여행지 성향 점수를 생성한다. 여행지 성향 점수와 여행지별 성향을 고려하여 최종 여행지를 추천한다.

• Journal of Gifted/Talented Education
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• v.25 no.4
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• pp.547-563
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• 2015

This paper aims at figuring out specific characteristics of affective attitude of gifted and talented in information, predicting follow-up activities and desirable direction of learning. Based on the analysis of this paper as educational directions and suggestions for elementary gifted and talented students in information are as follows: First, in gender ratio of gifted and talented in information, including the fact that ratio of boys is high, there remain the previous prejudice of higher information capability and it seems that girls who depend on external factors, parents and teachers should make more efforts to help girls trust their own capability in information science and lead them to give more value to attribution of efforts for achievement in information science. Second, as grade is higher, motivation to learn information science and attitude for success in information science among sub-elements of attitude to information science, motivation to seed positive recognition to higher graders is required. Third, in screening and selecting gifted and talented students in information, attitude to information science should be considered as main cause and the existing gifted and talented students in information should be prompted to improve their attitude to information science with value on effort for information science.

• Communications for Statistical Applications and Methods
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• v.17 no.1
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• pp.55-66
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• 2010

Propensity score adjustment(PSA) has been suggested as approach to adjustment for volunteer internet survey. PSA attempts to decrease the biases arising from noncoverage and nonprobability sampling in volunteer panel internet surveys. Although PSA is an appealing method, its application for internet survey regarding Korea presidential election and its effectiveness is not well investigated. In this study, we compare the Ni Korea internet survey with the telephone survey conducted by MBMR and KBS for 2007 Korean presidential election. The result of study show that the accuracy of internet survey can be improved by using PSA. And it is critical to include covariates that highly related to the voting tendency and the role of nondemographic variables seems important to improving PSA for Korea presidential election prediction.

• The Korean Journal of Applied Statistics
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• v.36 no.4
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• pp.323-335
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• 2023

In causal analysis of high dimensional data, it is important to reduce the dimension of covariates and transform them appropriately to control confounders that affect treatment and potential outcomes. The augmented inverse probability weighting (AIPW) method is mainly used for estimation of average treatment effect (ATE). AIPW estimator can be obtained by using estimated propensity score and outcome model. ATE estimator can be inconsistent or have large asymptotic variance when using estimated propensity score and outcome model obtained by parametric methods that includes all covariates, especially for high dimensional data. For this reason, an ATE estimation using an appropriate dimension reduction method and semiparametric model for high dimensional data is attracting attention. Semiparametric method or sparse sufficient dimensionality reduction method can be uesd for dimension reduction for the estimation of propensity score and outcome model. Recently, another method has been proposed that does not use propensity score and outcome regression. After reducing dimension of covariates, ATE estimation can be performed using matching. Among the studies on ATE estimation methods for high dimensional data, four recently proposed studies will be introduced, and how to interpret the estimated ATE will be discussed.

• Therapeutic Science for Rehabilitation
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• v.12 no.3
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• pp.61-77
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• 2023

Objective : This study analyzed the correlation between cognitive function and oral health-related quality of life (OHQoL). Methods : Demographic and clinical characteristics were extracted and utilized for subjects aged 45 years or older who participated in the 8th Korean Longitudinal Study on Aging in 2020. The dependent variable was the Geriatric Oral Health Assessment Index, and the independent variable was the level of cognitive function classified by the Mini-Mental State Examination scores. The analysis method used inverse probability of treatment weighting (IPTW). Then, the association between cognitive function and OHQoL was analyzed by multiple regression analysis. Results : Among the participants, 4,367 (71.40%) had normal cognition, 1,155 (18.89%) had moderate cognitive impairment, and 594 (9.71%) had severe cognitive impairment. As a result of analysis by applying IPTW, there was a negative correlation between the cognitive function group and OHQoL (normal vs. moderate: β = -2.534, p < .0001; normal vs. severe: β = -2.452, p < .0001). Conclusion : After propensity score matching, mild cognitive impairment showed a more negative association than severe cognitive impairment. Therefore, patients with cognitive impairment require oral health management education to improve OHQoL regardless of the level of cognitive impairment.

• Journal of Korean Elementary Science Education
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• v.41 no.2
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• pp.395-417
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• 2022

This study aims to analyze the correlation of creative personality, environment, process, and product as related to scientific creativity for different levels of elementary school students. We evaluated 105 fifth graders' responses to two tests: i) the scientific creativity test for creative process and product and ii) the self-report test for creative personality and environment. In the self-report test, creative personality comprises cognitive and affective personality, and creative environment constitutes home and school environments. To attain a deeper understanding of phenomena that cannot be explained by a quantitative analysis, interviews were conducted with four students who had the highest scores in creative product and four students who had the lowest scores in creative product while having higher-than-average scores in creative process. First, correlation of creative personality and environment were not significant. Second, in the interviews, students who had the highest scores in scientific creativity had common characteristics, namely, the ability to endure current difficulties to achieve future success and the propensity to listen to other people's ideas critically. Third, students who had the highest scores in creativity hailed from families that respected their opinions, whereas students with the lowest scores belonged to families that disregarded or neglected their opinions. Finally, this study specifies the criteria that should be considered for affective and environmental aspects of scientific creativity education.