• International Journal of Reliability and Applications
• /
• v.5 no.4
• /
• pp.129-145
• /
• 2004

We use a novel, forced censoring technique that closer fits the lower tails of strenth distributions to better estimate extremly smaller percentiles for measuring progress in continuous improvement initiatives. These percentiles are of greater interest for companies, government oversight organizations, and consumers concerned with safely and preventing accidents for many products in general, but specifically for medium density fiberboard (MDF). The international industrial standard for MDF for measuring highest quality is internal bond (IB, also called tensile strengh) and its smaller percentiles are crucial, especially the first percentile and lower ones. We induce censoring at a value just above the median to weight lower observations more. Using this approach, we have better fits in the lower tails of the distribution, where these samller percentiles are impacted most. Finally, bootstrap estimates of the small percentiles are used to demonstrate improved intervals by our forced censoring approach and the fitted model. There was evidence from the study to suggest that MDF has potentially different failure modes for early failures. Overall, our approach is parsimonious and is suitable for real time manufacturing settings. The approach works for either strengths distributions or lifetime distributions.

• The Journal of Pediatrics of Korean Medicine
• /
• v.23 no.2
• /
• pp.131-144
• /
• 2009

Objectives : The purpose of this study is to have better data and to make efficient clinical reviews on pre-school children's growth based on two measurements; Body composition for measuring body volume and bone age for potential growth. Methods : The study was conducted with 221 children(118 of boys and 103 of girls) from three kindergartens. Body compositions(soft lean mass, body fat mass, percent body fat) were measured by bioelectrical impedance analysis, bone age was measured by bone density through ultrasonic image of calcaneus. Results and Conclusions : 1. The higher level on weight or BMI, the more averages of soft lean mass, body fat mass, percent body fat. 2. The average bone ages and bone age-chronological age were lower in under 50 percentile's group, but it was higher in upper 50 percentile's group. Also, children with high BMI had older in bone ages and bone age-chronological age. 3. The higher in height percentile based on the bone age; there were more soft lean mass. 4. The averages of bone age and bone age-chronological age were significantly decreased, the more percentiles of height according to bone age were big, they were higher than total average in under 50 percentile's group of height, lower than total average in over 50 percentile's group of height in both boys and girls. 5. The average of MPH were significantly decreased in top percentiles of children's height distribution. Also, in the upper percentiles of height distribution based on bone age were big in only boys. 6. The body compositions(soft lean mass, body fat mass, percent body fat) were related to body volume growth, which can he measured by weight or BMI. The bone age, bone age-chronological age, and MPH were related in terms of hight. The body volume growth was a little hit related with potential growth.

• International Journal of Reliability and Applications
• /
• v.7 no.1
• /
• pp.27-39
• /
• 2006

Many real world cases in material failure analysis do not follow perfectly the normal distribution. Forcing of the normality assumption may lead to inaccurate predictions and poor product quality. We examine the failure process of the internal bond (IB or tensile strength) of medium density fiberboard (MDF). We propose a forced censoring technique that closer fits the lower tails of strength distributions and better estimates extremely smaller percentiles, which may be valuable to continuous quality improvement initiatives. Further analyses are performed to build an accelerated common-shaped Weibull model for different product types using the $JMP^{(R)}$ Survival and Reliability platform. In this paper, a forced censoring technique is implemented for the first time as a software module, using $JMP^{(R)}$ Scripting Language (JSL) to expedite data processing, which is crucial for real-time manufacturing settings. Also, we use JSL to automate the task of fitting an accelerated Weibull model and testing model homogeneity in the shape parameter. Finally, a package script is written to readily provide field engineers customized reporting for model visualization, parameter estimation, and percentile forecasting. Our approach may be more accurate for product conformance evaluation, plus help reduce the cost of destructive testing and data management due to reduced frequency of testing. It may also be valuable for preventing field failure and improved product safety even when destructive testing is not reduced by yielding higher precision intervals at the same confidence level.

• Journal of Forest and Environmental Science
• /
• v.32 no.3
• /
• pp.280-290
• /
• 2016

Stem diameter variability is an essential inventory result that provides useful information in forest management decisions. Little has been done to explore the modelling potentials of standard deviation (SDD) and coefficient of variation (CVD) of diameter at breast height (dbh). This study, therefore, was aimed at developing and testing models for predicting SDD and CVD in stands of Pinus caribaea Morelet (pine) in south west Nigeria. Sixty temporary sample plots of size $20m{\times}20m$, ranging between 15 and 37 years were sampled, covering the entire range of pine in south west Nigeria. The dbh (cm), total and merchantable heights (m), number of stems and age of trees were measured within each plot. Basal area ($m^2$), site index (m), relative spacing and percentile positions of dbh at $24^{th}$, $63^{rd}$, $76^{th}$ and $93^{rd}$ (i.e. $P_{24}$, $P_{63}$, $P_{76}$ and $P_{93}$) were computed from measured variables for each plot. Linear mixed model (LMM) was used to test the effects of locations (fixed) and plots (random). Six candidate models (3 for SDD and 3 for CVD), using three categories of explanatory variables (i.e. (i) only stand size measures, (ii) distribution measures, and (iii) combination of i and ii). The best model was chosen based on smaller relative standard error (RSE), prediction residual sum of squares (PRESS), corrected Akaike Information Criterion ($AIC_c$) and larger coefficient of determination ($R^2$). The results of the LMM indicated that location and plot effects were not significant. The CVD and SDD models having only measures of percentiles (i.e. $P_{24}$ and $P_{93}$) as predictors produced better predictions than others. However, CVD model produced the overall best predictions, because of the lower RSE and stability in measuring variability across different stand developments. The results demonstrate the potentials of CVD in modelling stem diameter variability in relationship with percentiles variables.

• Korean Journal of Community Nutrition
• /
• v.25 no.2
• /
• pp.150-158
• /
• 2020

Objectives: This study was conducted to estimate usual meat intake distribution, which may have been over/underestimated when estimations were made using only the third food codes of the Korea National Health and Nutrition Examination Survey (KNHANES). Methods: For this purpose, 24-hour recall data from the 2009 Korea National Health and Nutrition Examination Survey, which conducted a partial 2-day survey of food intake, were used. The Multiple Source Method (MSM) was used to estimate the distribution of the usual intake of red and processed meats. Results: The results of this study show that the mean intake of red meat was 45.07 g while that of processed meat was 4.33 g. These results are slightly higher than the consumption calculated using only tertiary food code, and the difference was statistically significant. Furthermore, characteristics of the estimated usual intake distribution were a smaller standard deviation, increased lower percentiles, and decreased upper percentiles compared to the 2-day mean intake distribution for both red and processed meats. The proportion of individuals not consuming red meat decreased substantially from approximately 37% to 0.7%. The proportion of consumption that exceeded 90 g, which is the upper limit of red meat intake recommended by the National Health Service (NHS), was only approximately 10% in the distribution of usual intake. Conclusions: As the consumption of processed foods is expected to continuously increase, caution is needed regarding the processes used to calculate food (group) intake to avoid over/underestimation. Moreover, use of KNHANES data to calculate the proportion of the population at risk of insufficiency or excess intake of certain nutrients or food (group), based on one day intake that does not address within-individual variation, may lead to biased estimates.

• Journal of Nutrition and Health
• /
• v.33 no.3
• /
• pp.279-288
• /
• 2000

The study examined BMIs, physical strength, activities, and the attitudes and behavior toward weight control among 7,968 Korean students{2,435 5th graders from elementary schools(ESs), 2,524 2nd graders from middle schools(MSs), 2,739 2nd graders from high schools(HSs)} nationwide. Compared to the 1987 data, there were increases of height(3-6cm) and weight(3-8kg), but decreases of physical strength and exercise. Lack of 'regular exercise' among girls from MSs and HSs and higher proportion of time spent on watching TV and using a computer for elementary schoolers were particularly noticeable. Proportions of students who were satisfied with their body weight were 49% for ESs, 35% for MSs, and 29% for HSs. There was no relationship between subjective and objective evaluations of body weight. Diet rather than exercise was more frequently chosen as a method of weight control. Compared to boys, girls showed stronger association between the amount of exercise and the subjective body weight in MSs and HSs, however this association was not found for the subjects from HSs. Values for the 50th percentile of BMI of boys and girls were 18.4 and 17.7 for ESs, 19.9 and 20.1for MSs, and 21.4 and 20.6 for HSs. In MSs and HSs, boys with BMI between 15th to 85th percentiles were physically stronger than those whose BMIs were lower than 15th kor higher than 85th percentiles. For the other groups, there was a trend of a positive relationship between BMI and physical strength. Based on the analyses of BMI and physical strength, this study suggests 22 and 21 for upper grades in ESs, 24 and 23 for MSs, and 27 and 25 for HSs as the respective cut off points of BMI for weight control n boys and girls. A need for implementing nutrition education program focused on weight control is also suggested.

• Journal of the Korean Academy of Child and Adolescent Psychiatry
• /
• v.8 no.1
• /
• pp.43-49
• /
• 1997

This study was designed to explore whether the temperament of a child influences the physical growth. The Korean version of the Parent Questionnaire for Children developed by Thomas, Chess and Korn was applied to 395 Korean children whose ages ranged from 3 years to 7 years. Simultaneously the height and the weight were measured for each child and converted into percentile scale according to the Growth Curve and the Weight Percentile Table for the Height of Korean children. Statistical analysis was performed among 9 temperamental categories, height and weight percentiles for the age and weight percentiles for the height using the first-order partial correlation analysis, controlling for the familial mean income per month. Results showed that the more temperamentally difficult a child is, the lower weight he has when compared with the children of the same age or the same height. Although there were some differences, the tendency of the above findings was maintained both in male and female children. These results show that the temperament may influence the physical growth as well as the psychological development.

• Journal of The Korean Association For Science Education
• /
• v.30 no.1
• /
• pp.68-79
• /
• 2010

This study utilized the What Is Happening In this Class (WIHIC) questionnaire to examine students' perceptions of their science learning environment. Data was collected from 587 middle school students in seven coeducation schools in Seoul. Higher mean scores occurred on the scales of Student cohesiveness, Task orientation, Cooperation and Equity in the WIHIC, whereas lower mean scores occurred on Teacher support, Involvement and Investigation. The effects of gender on students' perceptions of their science learning environment were not statistically significant overall, but girls perceived Student cohesiveness and Cooperation more positively than boys. Correlations between the WIHIC scales of the low-level group that perceived their learning environments negatively (10 percentiles) and the high-level group that perceived their learning environments positively (90 percentiles) were computed. Teacher support, Involvement, Task Orientation and Investigation were highly correlated with each other in the low-level group, whereas only Teacher support and Equity were correlated in the high group. Educational implications were discussed.

• Journal of Preventive Medicine and Public Health
• /
• v.32 no.1
• /
• pp.80-87
• /
• 1999

Objectives. The Study of Small Area Variation(SAV) is most interesting issue in the health care researches. Most studies of SAV have been concluded the existences of variation on the basis of the magnitude of variation without statistical testing. But it is difficult to explain the existence of variation with this way because variation indicies are easily influenced by several parameters and also their distribution are skewed. So, it needs for the study to investigate the distribution of these indices and develop the statistical testing model. Methods. This study was planned to analyze on the distribution of variation indices such as Extremal Quotient(EQ), Coefficient of Variation(CV), Systematic Component of Variation(SCV) and compare the statistical power among indicies. The simulations was performed on the basis of several assumptions and compared to the empirical data. Results. Main findings can be summarized as follows. 1. If other conditions are constant, the more number of regions, the larger 95 percentile of EQ. But under same situation, 95 percentile of CV and SCV were slightly decreased. 2. If the size of regional population or utilization rate were increased, 95 percentile of all statistics were decreased. Also in the cases of small population size and low utilization rate, 95 percentiles of EQ showed various change contrast to the little change of CV. 3. If the difference at the size of regional population were increased, 95 percentiles of EQ and SCV were increased contrast to the little different of CV. 4. If the utilization rate were increased, 95 percentiles of all indicies were increased. But under the same difference of utilization rate, the power of CV and SCV were increased comparing to no change of the power of EQ. 5. Usually the power of EQ were lower than that of CV or SCV and it is similar between CV and SCV. Conclusions. Therefore, we suggest that in selecting the variation indicies at the SAV, CV or SCV are superior than EQ in terms of significance level and power.

• Korean Journal of Community Nutrition
• /
• v.24 no.6
• /
• pp.465-475
• /
• 2019

Objectives: This study investigated dietary and lifestyle factors associated with the weight status among Korean adolescents in multicultural families. Methods: This cross-sectional study analyzed 1,751 multicultural families' adolescents who participated in the 2017-2018 Korea Youth Risk Behavior Surveys. Information on dietary and lifestyle factors was self-reported using a web-based questionnaire and this information included breakfast and foods consumption, perceived health status, alcohol drinking, smoking, physical activity, and weight control efforts. Body mass index (BMI) was calculated based on the self-reported height and body weight (kg/㎡). Weight status was assessed according to the 2017 Korean National Growth Chart: underweight (weight-for-age <5^th percentiles), overweight (85^th≤ BMI-for-age <95^th percentiles), and obese (BMI-for-age ≥95^th percentiles). Multiple logistic regression analysis was performed to examine the dietary and lifestyle factors associated with weight status after adjustment for covariates. Results: Among Korean adolescents from multicultural families, the prevalence of overweight/obesity was 20.9%, whereas about 7% of adolescents were underweight. The weight status did not show differences according to gender, school level, area of residence, and household income. Compared to adolescents who did not have breakfast during the previous week, those who had breakfast 3-4 days/week and ≥5 days/week had a 42% (p=0.021) and a 37% (p=0.009) lower prevalence of overweight/obesity, respectively. The adolescents who frequently consumed carbonated soft drinks (≥5 times/week) showed an odds ratio (OR) of 1.69 (95% CI=1.01-2.83) for overweight/obesity relative to those adolescents who did not consume carbonated soft drinks. The OR of being underweight for adolescents who ate fast food ≥3 times/week was 1.97 (95% CI=1.04-3.71) compared to those adolescents who had not eaten fast food during the previous week. Conclusions: Dietary and lifestyle factors were associated with overweight/obesity as well as underweight among Korean adolescents in multicultural families. Our findings could be used to design and provide nutrition interventions for this specific population.