• Journal of the Korean Data and Information Science Society
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• v.27 no.2
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• pp.337-351
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• 2016

There exist many real situations that statistical decision problems are classified into more than two categories. In these cases, the concordance statistics by the pair approach are mostly used. However, the expression of the classification of categories are ambiguous. Recently, the standardized evaluation data and re-expressed concordance statistics are defined and could be explained their meanings. They have still some non-specific problems for standard criteria of the statistics. Since these can be considered between result and truth categories additionally, two alternative concordance statistics might be proposed in this paper. Some advantages are founded that the proposed statistics could be discriminated all possible cases for two randomly selected categories. Moreover since the proposed statistics are represented with indicator functions, these could be transformed non-parametrically, so that these concordances are used for hypothesis testing.

• Communications for Statistical Applications and Methods
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• v.30 no.6
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• pp.577-587
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• 2023

Conventional categorical data imputation techniques, such as mode imputation, often encounter issues related to overestimation. If the variable has too many categories, multinomial logistic regression imputation method may be impossible due to computational limitations. To rectify these limitations, we propose a two-stage imputation method. During the first stage, we utilize the Boruta variable selection method on the complete dataset to identify significant variables for the target categorical variable. Then, in the second stage, we use the important variables for the target categorical variable for logistic regression to impute missing data in binary variables, polytomous regression to impute missing data in categorical variables, and predictive mean matching to impute missing data in quantitative variables. Through analysis of both asymmetric and non-normal simulated and real data, we demonstrate that the two-stage imputation method outperforms imputation methods lacking variable selection, as evidenced by accuracy measures. During the analysis of real survey data, we also demonstrate that our suggested two-stage imputation method surpasses the current imputation approach in terms of accuracy.

• The Korean Journal of Applied Statistics
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• v.15 no.2
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• pp.297-310
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• 2002

Liang and Zeger proposed generalized estimating equations(GEE) for analyzing repeated data which is discrete or continuous. GEE model can be extended to model for repeated categorical data and its estimator has asymptotic multivariate normal distribution in large sample sizes. But GEE is based on large sample asymptotic theory. In this paper, we study the properties of GEE estimators for repeated ordinal data in small sample sizes. We generate ordinal repeated measurements for two groups using two methods. Through Monte Carlo simulation studies we investigate the empirical type 1 error rates, powers, relative efficiencies of the GEE estimators, the effect of unequal sample size of two groups, and the performance of variance estimators for polytomous ordinal response variables, especially in small sample sizes.

• The Korean Journal of Applied Statistics
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• v.10 no.1
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• pp.151-161
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• 1997

An easy Monte Carlo Gibbs sampling approach is suggested for Bayesian analysis of cumulative logit models for ordinal polytomous data. Because in the cumulative logit model the posterior conditional distributions of parameters are not given in convenient forms for random sample generation, appropriate latent variables are introduced into the model so that in the new model all the conditional distributions are given in very convenient forms for implementation of the Gibbs sampler.

• Journal of Microbiology
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• v.35 no.2
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• pp.79-86
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• 1997

For the phylogenetic study of the genus Trichaptum, nuclear ribosomal DNA sequences from eight strains of four Trichaptium species were examined. Phylogenetic trees were constructed using molecular data on 18 rDNA and 5.8S rDNA and thei ITSs. Parsimony analyses of the Trichaptum species showed that T. biforme and T. laricinum made a monophyletic group respectively, suggesting that each species is phylogenetically independent. However, T. abietum represented a polyphyletic group and T. fusco-violaceum formed a polytomous group, suggesting that these species could be in the process of evolutionary differentiation. Examination of base substitutions of the 18S rRNA gene reveals that the C-T transition is most predominant and that there is a stronger transition bias between closely related organisms rather than between distantly related ones.

• Communications for Statistical Applications and Methods
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• v.2 no.2
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• pp.176-183
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• 1995

Mean opinion score (MOS) method has been used in many areas to quantify opinions of respondents not only in survey research but in evaluating the parameters of population that are not measurable of are technically hard to be measured. Histogram is an important graphical technique because of the role it plays in describing categorical data as well as quantitative. In MOS method, subjective opinions of respondents are quantified by opinion scores and the arithmetic means of opinion scores have been used to describe the interesting population. Since opinion scores are polytomous, the values of arithmetic means have little meanings. In this paper, cumulative percentage curves as a function of the means of opinion scores are derived by combining means of opinion scores and histograms. It is proposed for better interpretation to opinion scores in MOS method, one of subjective evaluation methods.

• Journal of Preventive Medicine and Public Health
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• v.32 no.3
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• pp.325-332
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• 1999

Objectives: The aim of this study is to identify major factors associated with physical functioning among the Korean elderly. Methods: Data come from a survey of a nationally representative sample of 2,058 older people aged 60 years or elder living in the community. A hierarchical functioning scale was constructed, using upper and lower body mobility, IADLs, and ADLs. Socioeconomic characteristics, chronic conditions, measures of health status, health service use, and social support were analyzed to explore their influence on functioning. Polytomous logistic regression analysis was conducted to identify major contributing factors to different levels of functioning. Results: Persons of older age, female, with chronic diseases (heart disease, stroke, fracture/dislocation) were consistently more likely to show a higher degree of functional limitation. There were variations, however, among other factors; e.g., those with arthritis were more likely to be only mildly impaired, but not moderately or severely impaired. Conclusions: Older Korean adults living in the community with impaired functioning constitute persons with diverse characteristics. Policy and program activities need to address specific needs of older people in different functioning states.

• Journal of Science Education
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• v.41 no.1
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• pp.16-35
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• 2017

This study attempted to investigate the relationship among engineering students' creativity, engineering education accreditation, gender, and academic year. To be specific, fist, we examined the validity and reliability of the instrument for measuring engineering students' creativity by conducting Rasch analysis. Second, we compared level of creativity in terms of gender, academic year, and engineering education accreditation by using three-way ANOVA. Third, correlations among four constructs of creativity were examined. Fourth, latent classes with respect to creativity within the participants were identified using polytomous latent class analysis (poLCA). Data were collected from 2098 engineering students by using instrument for measuring four different constructs (creative cognition, creative tendency, collaboration, environment). By using Rasch analysis, validity and reliability of instrument for measuring creativity were confirmed. And the results of three-way ANOVA showed that there were significant difference in creativity in terms of gender. Female students showed the low level of creativity compared with male students. Also there were significant difference in creativity except creative cognition factor in terms of academic year. But there were no significant difference in creativity between students who participated engineering education accreditation program and the others. All constructs of creativity were significantly correlated with each others. Lastly, poLCA results showed that there were three distinct subgroups within engineering students in terms of the level of creativity. In the subgroup with low creativity, there were more female and first year students. Based on these findings, we discussed education for engineering students' creativity.