• Communications for Statistical Applications and Methods
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• v.21 no.5
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• pp.363-386
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• 2014

This paper has improved several ratio type estimators of the population median including their generalization in the presence of three known quartiles of an auxiliary variable. The properties of the improved estimators are discussed and applied. Both the empirical and simulation studies confirm that our new estimators perform efficiently.

• Nutrition Research and Practice
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• v.4 no.2
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• pp.142-148
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• 2010

The food frequency questionnaire (FFQ) has been used as an important dietary assessment tool in epidemiologic studies, but the usefulness of the FFQ has been debated in recent years. This study was performed to evaluate the relative validities of 3-day food records and the semi-quantitative FFQ. A total of 124 subjects finished 3-day food records (FRs) during each of the four seasons, as well as the FFQ from December 2002 to May 2004. The FFQ was a food based semi-quantitative FFQ including 103 items. Three-day FRs from each season and a randomly selected season were compared with the remaining 9-day FRs. The remaining 9-day FRs, as a reference measurement, were also compared with the FFQ. Pearson's correlation coefficients between the 3-day FRs and the 9-day FRs were between 0.14 and 0.56. Pearson's correlation coefficients between the FFQ and the 9-day FRs ranged between 0.07 and 0.41. Average proportions of classification into the same quartiles, adjacent quartiles, and distant quartiles between the 3-day FRs and the 9-day FRs were 35.8%, 40.5%, and 5.2%, respectively. On average, the proportions of classification into the same quartiles, adjacent quartiles, and distant quartiles between the FFQ and the 9-day FRs were 31.1%, 39.4%, and 6.9%, respectively. Three-day FRs showed higher correlations and higher agreement proportions of quartile classification with the 9-day FRs than did the FFQ, but both relative validities of 3-day FRs and the FFQ appear to be acceptable as dietary assessment tools. Further studies for validating food intake by reliable biomarkers are necessary.

• Journal of Korean Society for Quality Management
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• v.26 no.3
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• pp.150-155
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• 1998

It is necessary to describe a data set after collection of data in elementary statistics course. Two major numerical summary of the data set may be measures of central location and dispersion. There are various unmerical summary methods in presenting how data are dispersed and each method has its own advantages and disadvantages. Quartiles are discussed among several methods to describe dispersion of data set. When data type is discrete, exact quartile values are sometimes ambiguous to find, whereas exact quartile values are obtained for contionuous data. Examples of both data types are given. Programs listed below may be used to provide quartiles in MINITAB and SAS.

• Journal of the Korean Society of Food Culture
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• v.36 no.4
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• pp.349-361
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• 2021

This study was conducted to investigate the dietary adaptation and use of the university foodservice (UF) in Korea according to the residence period of foreign students. The average length of residence in Korea of t he subjects was 8.2 months. The period of residence was divided into quartiles: 1-4 months in the first quartile (average 2.2 months), 5-7 months in the second quartile (average 6.3 months), 8 months in the third quartile, and 9-66 months in the fourth quartile (average 18.3 months). The regularity of meals tended to be the highest in the 1st quartile and lowest in the 2nd quartile and then increased in the 3rd and 4th quartiles. The frequency of consumption of delivery food and convenience store food was lowest in the first quartile and highest in the second quartile and then decreased with the period of residence. The frequency of night eating increased according to the period of residence after the second quartile. The degree of adaptation to Korean foods was highest in the first quartile. The use of the university cafeteria was significantly higher in the 1st and 4th quartiles than in the 2nd and 3rd quartiles (p<0.05, p<0.01, respectively). The satisfaction with the UF decreased as the residence period increased. Based on these results, since international students are very positive and try to adapt to the dietary life in Korea in their early years of studying in Korea, it would be desirable to intensively support them to adjust to their dietary life at this time. In addition, since it takes about 18 months or more to assimilate the Korean food culture and show positive changes, it is necessary to continuously operate the Korean food culture adaptation program for international students over this period.

• Journal of Preventive Medicine and Public Health
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• v.45 no.3
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• pp.181-187
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• 2012

Objectives: Serum uric acid levels have been reported to be associated with a variety of cardiovascular conditions. However, the direct association between uric acid levels and metabolic syndrome remains controversial. Thus, we evaluated the association of serum uric acid levels and metabolic syndrome in a community-based cohort study in Korea. Methods: We performed cross-sectional analysis of baseline data of 889 males and 1491 females (aged 38 to 87) who participated in baseline examinations of the Korean Genome and Epidemiology Study: Kanghwa study. Blood samples were collected after at least an 8 hour fast. Uric acid quartiles were defined as follows: <4.8, 4.8-<5.6, 5.6-<6.5, ${\geq}6.5$ mg/dL in males; and <3.8, 3.8- <4.3, 4.3 - <5.1, ${\geq}5.1$ mg/dL in females. Metabolic syndrome was defined by the National Cholesterol Education Program Adult Treatment Panel III Criteria with adjusted waist circumference cutoffs (90 cm for males; 80 cm for females). The association between serum uric acid quartiles and metabolic syndrome was assessed using multivariate logistic regression. Results: The odds ratio for having metabolic syndrome in the highest versus lowest quartiles of serum uric acid levels was 2.67 (95% confidence interval [CI], 1.60 to 4.46) in males and 2.14 (95% CI, 1.50 to 3.05) in females after adjusting for age, smoking, alcohol intake, body mass index, total cholesterol, HbA1c, albumin, ${\gamma}$-glutamyltransferase, blood urea nitrogen, and log C-reactive protein. The number of metabolic abnormalities also increased gradually with increasing serum uric acid levels (adjusted p for trend < 0.001 in both sexes). Conclusions: Higher serum uric acid levels are positively associated with the presence of metabolic syndrome in Korean males and females.

• Nutrition Research and Practice
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• v.12 no.3
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• pp.222-232
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• 2018

BACKGROUND/OBJECTIVES: Since gain or loss of skeletal muscle mass is a gradual event and occurs due to a combination of lifestyle factors, assessment of dietary factors related to skeletal muscle is complicated. The aim of this study was to investigate the changes in total energy intake according to the level of skeletal muscle mass. SUBJECTS/METHODS: A total of 8,165 subjects ${\geq}30years$ of age from the Korean National Health and Nutrition Examination Surveys (KNHANES) 2008-2011 were included in the analysis, and multivariate-adjusted regression analyses were performed to analyze the association of the quartiles of sarcopenia index (SI) with energy intake of the study population after adjusting for age and metabolic parameters. RESULTS: The increase in SI quartile was in proportion to the gradual decrease in systemic lipids and the anthropometric measurement of fat accumulation (P < 0.001). Subjects in higher SI quartiles tended to consume more total energy and energy-producing nutrients than those in lower quartiles (P < 0.001). After age, body weight, alcohol consumption, and metabolic parameters were adjusted in the analysis, total energy intake gradually increased according to the increase in SI quartile, and the association between total energy intake and SI was more pronounced in men. However, the risk (odd ratio) of having a low SI was not affected by any single macronutrient intake. CONCLUSION: In this study, total energy intake was positively associated with SI and relative skeletal mass in both men and women. However, no significant association or a weak association was observed between any single macronutrient intake and skeletal muscle mass. The data indicated that acquiring more energy intake within the normal range of energy consumption may help to maintain skeletal muscle mass.

• Annals of Occupational and Environmental Medicine
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• v.35
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• pp.40.1-40.10
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• 2023

Background: Efforts for the prevention and management of cardiovascular diseases (CVDs) in workers have been actively pursued. Obesity is one of the important risk factors related to CVDs. Obesity has various metabolic characteristics, and some individuals can be metabolically healthy. Body composition including skeletal muscle mass is known to have protective effect in obesity. The study aims to investigate the association between skeletal muscle mass and Korea Occupational Safety and Health Agency (KOSHA) CVD risk among obese male manufacturing workers in Korea and to identify appropriate indicators of skeletal muscle mass for predicting risk of CVDs. Methods: The study was conducted on 2,007 obese male workers at a manufacturing industry aged more than 19 years. Skeletal muscle mass, skeletal muscle index (SMI), skeletal muscle mass percent (SMM%) and skeletal muscle to body fat ratio (MFR) were used to evaluate body composition and these indicators were divided into quartiles. The odds ratios (ORs) and 95% confidence intervals (CIs) for the KOSHA CVD risk groups according to quartiles of skeletal muscle mass indicators were estimated using ordinal logistic regression analysis. Results: The OR for the KOSHA CVD risk groups in the highest quartile of SMI was 1.67 (95% CI: 1.42-1.92), while the ORs for the KOSHA CVD risk groups in the highest quartiles of SMM%, SMM/body mass index (BMI), and MFR were 0.47 (95% CI: 0.22-0.72), 0.51 (95% CI: 0.05-0.76), and 0.48 (95% CI: 0.23-0.74), respectively. Conclusions: We found that high SMI increase the likelihood of high risk of CVDs, while high SMM%, SMM/BMI, and MFR lower the likelihood of high risk of CVDs. Accurate evaluation of skeletal muscle mass can help assess the cardiovascular risk in obese male workers.

• The Korean Journal of Applied Statistics
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• v.19 no.1
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• pp.81-96
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• 2006

This paper proposes a simple control chart method which can be practically used for asymmetric process data where the distribution is unknown. If we use the Shewhart type control charts which are based on normality assumption for the asymmetric process data, the type I error could increase as the asymmetry increases and the effectiveness of control chart to control variation decreases. To solve such problems, this paper suggests to calculate the control limits based on the quartiles. If we obtain the control limits by such quartile method, the type I error could decrease and it looks much more practical for asymmetric distributed process data.

• Nutrition Research and Practice
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• v.10 no.1
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• pp.81-88
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• 2016

BACKGROUND/OBJECTIVES: Serum ferritin levels are significantly increased after menopause and greatly affect women's health. The aim of this study was to investigate the dietary and non-dietary factors associated with high ferritin levels in postmenopausal women. SUBJECTS/METHODS: Among adult women in 2010-2012, qualified postmenopausal women (n = 3880) were separated into quartiles of serum ferritin. The variable differences among the quartiles of ferritin were determined using either procsurvey chi-square test (${\chi}^2$-test) among categorical variables, or GLM (Generalized Linear Model) among continuous variables. The odds ratio for high ferritin in relation to dietary factors was also determined using procsurvery logistic analysis. RESULTS: Age, obesity, drinking habit, and blood glucose levels were found to be significant indicators of high serum ferritin level after adjusting for all confounding factors. Among the food groups, grain, milk, vegetable, and seaweed intakes were significantly associated with high ferritin levels, but after adjusting for all confounding factors, only grains and vegetables remained significant factors. Among the nutrient groups, calcium, vitamin A, and vitamin C intake were significant factors, but after adjustment, none of the nutrient groups analyzed were associated with a high risk of ferritin. CONCLUSION: Age, obesity, drinking habit, and glucose levels, as well as inadequate intakes of grains and vegetables, were found to be significantly associated with high serum ferritin levels in postmenopausal Korean women.

• Nutrition Research and Practice
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• v.16 no.1
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• pp.94-105
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• 2022

BACKGROUND/OBJECTIVES: The purpose of this study was to investigate the association between socioeconomic status and chewing discomfort and identify the role of food insecurity in the association's causal pathway in a representative sample of Korean elders. MATERIALS/METHODS: We conducted cross-sectional analyses of the Korea National Health and Nutrition Examination Survey (2013-2015) data for elders aged ≥ 65 years. Socioeconomic status indicators used included household income and education level. Chewing discomfort was assessed according to the self-reported presence of chewing problems. Food security was surveyed using a questionnaire based on the US Household Food Security Survey Module. RESULTS: The odds ratios of chewing discomfort in the 1st and 2nd income quartiles were 1.55 (95% confidence interval [CI], 1.15-2.10) and 1.40 (95% CI, 1.03-1.90), respectively, compared to participants in the highest income quartile. Participants with the lowest education level were 1.89 (95% CI, 1.30-2.75) times more likely to have chewing discomfort than those without chewing discomfort. After including food security in the final model, the logistic coefficients were attenuated in the income and education quartiles. CONCLUSIONS: Low socioeconomic status was associated with chewing discomfort. In addition, the results confirm that food insecurity can mediate the association between socioeconomic inequalities and chewing discomfort among the elderly.