• Journal of Korean Institute of Industrial Engineers
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• v.25 no.4
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• pp.510-516
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• 1999

This paper proposes methods of estimating lifetime distribution from incomplete field data under parametric regression models. Failure-record data-failure times and covariates-reported to the manufacturer can be seriously incomplete for satisfactory inference since only reported failures are recorded. This paper assumes that within-warranty data are reported with probability $P_1$ ($\leq1$) and after-warranty data are reported with Methods of obtaining pseudo and after-warranty data are reported with $P_2$ (< $P_1$). Methods of obtaining pseudo maximum likelihood estimators(PMLEs) are outlined, their asymptotic properties are studied, and specific formulas for Weibull distribution are obtained. Simulation studies are perfumed to investigate the effects of follow-up percentage on the PMLEs.

• Nutrition Research and Practice
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• v.7 no.4
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• pp.326-329
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• 2013

Height and weight are important indicators to calculate Body Mass Index (BMI); measuring height and weight directly is the most exact method to get this information. However, it is ineffective in terms of cost and time on large population samples. The aim of our study was to investigate the validity of self-reported height and weight data compared to our measured data in Korean children to predict obese status. Four hundred twenty-two fifth-grade (mean age $10.5{\pm}0.5$ years) children who had self-reported and measured height and weight data were final subjects for this study. Overweight/obese was defined as a BMI of or above the 85th percentile of the gender-specific BMI for age in the 2007 Korean National Growth Charts or a BMI of 25 or higher (underweight : < 5th, normal : ${\geq}5th$ to < 85th, overweight : ${\geq}85th$ to < 95th). The differences between self-reported and measured data were tested using paired t-test. Differences based on overweight/obese status were tested using analysis of variance (ANOVA) and linear trends. Pearson's correlation and Cohen's kappa were tested to examine agreements between the self-reported and measured data. Although measured and self-reported height, weight and BMI were significantly different and children tended to overreport their height and underreport their weight, the correlation between the two methods of height, weight and BMI were high (r = 0.956, 0.969, 0.932, respectively; all P < 0.001), and both genders reported their overweight/non-overweight status accurately (Cohen's kappa = 0.792, P < 0.001). Although there were differences between the self-reported and our measured methods, the self-reported weight and height was valid enough to classify overweight/obesity status correctly, especially in non-overweight/obese children. Due to bigger underestimation of weight and overestimation of height in obese children, however, we need to be aware that the self-reported anthropometric data were less accurate in overweight/obese children than in non-overweight/obese children.

• Journal of Preventive Medicine and Public Health
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• v.43 no.5
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• pp.396-402
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• 2010

Objectives: Self-reported anthropometric values, such as height and weight, are used to calculate body mass index (BMI) and assess the prevalence of obesity among adolescents. The aim of this study was to evaluate the validity of selfreported height, weight, and BMI of the Korea Youth Risk Behavior Web-based Survey questionnaire. Methods: A convenience sample of 137 middle school students and 242 high school students completed a selfadministered questionnaire in 2008. Body height and weight were directly measured after self-reported values were obtained from the questionnaire survey. Sensitivity, specificity, and kappa statistics were computed in order to evaluate the validity of the prevalence of obesity (BMI $\geq$ 95th percentile or $\geq$ $25;kg/$m^2$) based on self-reported data. Results: Self-reported weight and BMI tended to be underestimated. Self-reported height tended to be overestimated among middle school females and high school males. Obese adolescents tended to underestimate their weight and BMI and overestimate their height more than non-obese adolescents. The prevalence estimate of obesity based on selfreported data (10.6%) was lower than that based on directly measured data (15.3%). The estimated sensitivity of obesity based on self-reported data was 69.0% and the specificity was 100.0%. The value of kappa was 0.79 (95% confidence interval, 0.70 - 0.88). Conclusions: This study demonstrated that self-reported height and weight may lead to the underestimation of BMI and consequently the prevalence of obesity. These biases should be taken into account when self-reported data are used for monitoring the prevalence and trends of obesity among adolescents nationwide.

• Phonetics and Speech Sciences
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• v.4 no.1
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• pp.99-108
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• 2012

Recent research has identified that self-reported voice problems are a risk indicator for voice disorders. However, previous studies concerning the general population did not take into account the influence of gender on self-reported voice problems. The purpose of the present cross-sectional study was to determine the gender differences in risk factors of self-reported voice problems in the Korean adult population using national survey data. This study utilized data from the Korea National Health and Nutritional Examination Survey 2008. Subjects inclued 3,622 people (1,508 male and 2,114 female) aged 19 years and older living in the community. Data were analyzed using t-test, one-way ANOVA, and multiple logistic regression. The prevalence of self-reported voice problems was 5.9% in males, and 8.1% in females Females had higher incidents of self-reported voice problems than males. Adjusting for covariates, in males, age (OR=2.47, 95% CI: 1.07-5.70), pain and discomfort during the last two weeks (OR=3.64, 95% CI: 2.20-6.01) were independently associated with self-reported voice problems (p<0.05). In women, age (OR=1.96, 95% CI: 1.18-3.26), education (OR=2.09, 95% CI: 1.06-4.12), smoking (OR=2.70, 95% CI: 1.48-4.93), thyroid disorders (OR=2.58, 95% CI: 1.47-4.53), pain and discomfort during the last two weeks (OR=1.75, 95% CI: 1.21-2.54) were independently associated with self-reported voice problem (p<0.05). Self-reported voice problems related risk factors differed according to gender. These findings suggest that there needs to be different program strategies that reflect gender differences in self-reported voice problems.

• Korean Journal of Occupational Health Nursing
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• v.6 no.2
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• pp.136-143
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• 1997

The purpose of this study was to analyze relationship between the role conflict and self-reported climacteric symptoms in the middle-aged industrial female workers. The data were collected by self-reported questionnaire from Nov. 1 to Nov. 30, 1996. The subjects were 201 women whose age, between 40 and 59 years. The analysis of data was t-test, ANOVA, $Scheff{\grave{e}}$ test, Pearson correlation coefficient analysis, Stepwise multiple regression analysis. The results were as follows : 1. 54.8% of the respondents had their climacteric symptom in middle life. 2. Age and religion affected significantly self-reported climacteric symptoms(F=4.2, P=.007 ; t=-2.1, P=0.42). 3. A comparison between two groups, with high and low rate of self-reported climacteric symptoms, indicated that for middle-aged industrial female workers when role conflict is high, climacteric symptoms is high(t=7.8, P=.000). 4. The relationship between self-reported climacteric symptoms and role conflict was positively significant(r=.5, P=.000). 5. The role conflict as a spouse affected significantly self-reported climacteric symptoms(F=52.6, P=.000). Role conflict the role as a spouse was explained 21% of self-reported climacteric symptoms. In conclusion, role conflict is the dominant factor in influencing self-reported climacteric symptoms.

• Journal of Environmental Health Sciences
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• v.40 no.6
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• pp.492-501
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• 2014

Objectives: The purpose of this study was to assess the validity of self-reported cigarette smoking status and investigate factors associated with the accuracy self-reported and measured urinary cotinine in Korean adults. Methods: We used data from the $1^{st}$ Korean National Environmental Health Survey (2009-2011) among adults aged ${\geq}19$ years (N=6,246). The survey examined self-reported smoking status, and urinary cotinine was regarded as the biomarker of exposure to tobacco smoke. Urinary cotinine was analyzed using a gas chromatography-mass spectrometry (GC/MS) and data analysis was conducted using IBM SPSS version 20.0, which uses the sample weight and calculates variance estimates to adjust for the unequal probability of selection into the survey. Results: We calculated a cut-off point (53.3 ug/L) by using a ROC (Receiver Operating Characteristic) curve. The smoking prevalence was 24.6% based on self-reported data and 28.2% based on urinary cotinine concentrations. When we assessed the agreement between self-reported and urinary cotinine, we found an average agreement of 97.7% among self-reported smokers and 94.5% among self-reported non-smokers. Among self-reported smokers, factors affected the discrepancy were age, household economic status and average number of cigarettes smoked per day. On the other hand, gender, former smoking experience, and exposure to SHS (second hand smoke) were associated with discrepancies among self-reported non-smokers. Conclusion: These results suggest that self-reported data on smoking status provide a valid estimate of actual smoking status. In future research, we will conduct a continuous monitoring study for reliability verification of the data to reduce potential interpretation errors.

• Korean Journal of Adult Nursing
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• v.24 no.6
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• pp.607-614
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• 2012

Purpose: This is a descriptive research that reports incidents of workplace violence among care helpers. Methods: The subjects were 181 care helpers from elderly care facilities and domiciliary elderly welfare centers in Daejeon. Data were collected through self-administered questionnaires from July to November 2011. Subjects were asked to report incidents of violence within the previous six months. Data analysis included one-way ANOVA, and logistic regression analysis. Results: Forty-seven percent of care helpers reported verbal violence, 16% reported being physically threatened, more than 21 % reported sustaining a physical injury with 2% reporting severe physical injuries. Further, 18.8% of the care givers reported being sexually harassed by client. There were differences in reported workplace violence based on service types, service hours and whether there were policies about workplace violence. Conclusion: To prevent workplace violence for carehelpers, it is necessary to make a policy for preventing violence and develop a violence prevention program to meet service characteristics of facility-based and domiciliary care helpers.

• Korean Journal of Health Education and Promotion
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• v.18 no.3
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• pp.163-175
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• 2001

The purpose of this study is to collect fundamental data for weight control education based on obesity, weight control practices and body image in female college students. Those surveyed were 364 female college students attending universities in Seoul, Kyoung-Gi and Chung Cheung Buk Do. The data were collected from June 1, 1999 to September 10, 1999. The resulting data are as follows: 1. The mean BMI of the female college students was 19.78:t1.87kg/$\textrm{m}^2$, which comes within the range of normal weight. Underweight, normal weight and overweight students were respectively 27.2%, 66.8% and 5.5%. As many as 7.1% of the underweight students and 42.8% of the normal weight students described themselves as being "fatty". 2. Of these subjects, 83.5% reported wanting to lose weight, and the primary reason of weight control was to improve their appearance. The mean weight that they wanted to lose was 5.2$\pm$2.7kg, and 68.7% of the respondents had tried to lose weight. Among them, the most frequently reported weight control behavior was dieting followed by exercise, 30% reported fasting, 3.6% reported using drugs, 4.4% reported smoking and 3.6% reported vomiting. As to the weight loss effect, 96.7% of the subjects used behavior modification, 82.5% of the students exercised, and 76.1% of the dieters reported they had lost weight. 3. As to body image, many female college students were dissatisfied with their body figures, especially thighs(70.3%), hips(60.4%), abdomens(60.2%), and weight(55.2%). The body image of the students that perceived themselves as "fatty" was the lowest. 4. There were significant differences in the mean weight that they wanted to lose and the weight control attempts according to weight perception. Those that perceived themselves as "fatty" wanted to lose more weight, and had more weight control experiences. In conclusion, attempts at weight control are common in the female college students and many students appear to be dissatisfied with their body shapes. It is important to educate about healthy weight control methods and raise their awareness of the positive body image.ss of the positive body image.

• Journal of Environmental Health Sciences
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• v.48 no.4
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• pp.216-226
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• 2022

Background: The amount of smoking in adolescence increases with a younger age of smoking initiation and affects physical health. To establish and evaluate smoking-related policies, it is important to determine actual smoking status. Validation of self-reported questionnaires can identify the accuracy of the questionnaire data reflecting smoking status. Objectives: The purpose of this study was to evaluate the validity of self-reported smoking status and identify factors affecting the accuracy of self-reported smoking in South Korean adolescents. Methods: This study investigated the consistency between cotinine concentrations and self-reported questionnaire data through the analysis of urine samples collected from 922 adolescents aged 13~18 among the participants of Cycle 3 of the Korean National Environmental Health Survey. Smoking status was classified using the cotinine cut-off point of 39.85 ㎍/L in adolescents, and factors affecting the accuracy were analyzed through multiple logistic regression analysis. Results: The smoking rates according to the self-reported questionnaire and cut-off point-based cotinine concentrations among adolescents were 3.1% and 5.1%, respectively. The results found 97.1% consistency between self-reported smokers and smokers according to cotinine concentration. Factors affecting the discrepancy showed a significant relationship, including gender, secondhand smoke, and use of e-cigarettes. Conclusions: The results can be used as basic data to establish a smoking policy for adolescents through continuous monitoring and improvement of questionnaire items of factors affecting the discrepancy.

• Journal of Food Hygiene and Safety
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• v.2 no.4
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• pp.215-237
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• 1987

This study was conducted to prepare some information about food poisoning outbreaks in Korea. In this study, all reported data were reviewed, but the data during recent ten years (1977-1986) were mainly analyzed because of data shortage. We used three year moving averages in order to investigate the trend to food poisoning outbreaks, by year, foodborne pathogens, specific foods, and place food contaminated or mishandled.