• Communications for Statistical Applications and Methods
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• v.15 no.6
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• pp.843-858
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• 2008

BLS adjustment methods have been able to provide more accurate estimates of total and make samples represent population characteristics by post-adjustment of design weights of samples. However, BLS methods use additional data, for instance number of employee, without this information or using other information, give different weight adjustment factors. In this paper we studied the sensitivity of the variables used in BLS adjustment. The 2007 monthly labor survey data is used in analysis.

• Survey Research
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• v.12 no.3
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• pp.173-186
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• 2011

We introduced the methodologies used to construct the longitudinal weights and cross-sectional weight that are required for the analysis of Korea Youth Panel Survey. To analyze the longitudinal dynamic change of the population, we derived the longitudinal weight through nonresponse adjustment based on logistic regression and post-stratification. Cross-sectional weights that are necessary to produce an asymptotically unbiased estimator of the population parameter were constructed through simple nonresponse adjustment based on overall response rate and post-stratification.

• Proceedings of the Korean Statistical Society Conference
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• 2003.10a
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• pp.111-115
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• 2003

소지역 모형들은 고정된(fixed)효과와 랜덤 효과를 포함하는 일반적 선형 혼한 모형의 특별한 경우로 간주될 수 있다. 소지역 평균이나 종계는 고정된 효과와 랜덤 효과의 일치 결합으로 표현될 수 있다. 블록 대각 공분산 구조를 갖는 선형 혼합모형(mixed model) 아래서 EBLUP은 실재문제에 있어서 많이 소지역 모형에 응용된다. 설계 가중값(design weight) 들에 의존하고 설계-일치(design consistency) 성질을 만족하는 Pseudo-EBLUP 추정량들은 소지역추정에서 합해지면 (aggregated) 사후-수정(post-adjustment)없이 벤치마킹 성질을 만족한다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.10
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• pp.2142-2149
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• 2002

Contacting with ground in the post-card area size only, tire supports entire automobile weight. As well, it characterizes most of automobile running performance. Among the design parameters, the carcass contour becomes a key design factor. This paper deals with the time-effective optimal design of tire crown contour in order to improve the tire wear performance by employing a back-propagation neural network model.

• Journal of Korean Medical Science
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• v.33 no.48
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• pp.312.1-312.10
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• 2018

Background: Obesity is related to several comorbidities and mortality, but its relationship with acute kidney injury (AKI) and long-term mortality remain undetermined in patients undergoing coronary artery bypass grafting. Methods: Data from 3,018 patients (age ${\geq}18$ years) who underwent coronary artery bypass graft surgery from two tertiary referral centers were retrospectively reviewed between 2004 and 2015. Obesity was defined using the body mass index, according to the World Health Organization's recommendation. The odds and hazard ratios in post-surgical, AKI, and all-cause mortality were calculated after adjustment for multiple covariates. Patients were followed for $90{\pm}40.9$ months (maximum: 13 years). Results: Among the cohort, 37.4%, 2.4%, 21.1%, 35.1%, and 4.0% of patients were classified as normal weight, underweight, overweight-at-risk, obese I, and obese II, respectively. Post-surgical AKI developed in 799 patients (26.5%). Patients in the obese groups (overweight-at-risk to obese II) had a higher risk of AKI than did those in the normal-weight group. During the follow-up period, 787 patients (26.1%) died. Underweight patients had a higher risk of mortality than did normal-weight patients, whereas overweight-at-risk, obese I, and obese II patients showed better survival rates. Conclusion: After coronary artery bypass graft surgery, obese patients encountered a high risk of AKI, and underweight patients exhibited a low chance of survival. Awareness of both obese and underweight statuses should be raised in these patients.

• Communications for Statistical Applications and Methods
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• v.23 no.1
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• pp.47-55
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• 2016

Stratified cluster sampling has been widely used for effective parameter estimations due to reductions in time and cost. The probability proportional to size (PPS) sampling method is used when the number of cluster element are significantly different. However, simple random sampling (SRS) is commonly used for simplicity if the number of cluster elements are almost the same. Also it is known that the ratio estimator produces a good performance when the total number of population elements is known. However, the two stage cluster estimator should be used if the total number of elements in population is neither known nor accurate. In this study we suggest a composite estimator by combining the ratio estimator and the two stage cluster estimator to obtain a better estimate under a certain population circumstance. Simulation studies are conducted to compare the superiority of the suggested estimator with two other estimators.

• Pediatric Gastroenterology, Hepatology & Nutrition
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• v.24 no.6
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• pp.546-554
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• 2021

Purpose: Malnutrition is a significant issue for pediatric patients with cancer. We sought to evaluate the effectiveness and complication rate of percutaneous endoscopic gastrostomy (PEG) placement in pediatric oncology patients. Methods: A retrospective chart review was performed on 49 pediatric oncology patients undergoing PEG placement at Johns Hopkins All Children's Hospital between 2000 and 2016. Demographic and clinical characteristics, complications, absolute neutrophil count at time of PEG placement and at time of complications, length of stay, and mortality were identified. Weight-for-age Z-scores were evaluated at time of- and six months post-PEG placement. Results: The overall mean weight-for-age Z-score improved by 0.73 (p<0.0001) from pre- (-1.11) to post- (-0.38) PEG placement. Improvement in Z-score was seen in patients who were malnourished at time of PEG placement (1.14, p<0.0001), but not in those who were not malnourished (0.32, p=0.197). Site infections were seen in 12 (24%), buried bumper syndrome in five (10%), and tube dislodgement in one (2%) patient. One patient (2%) with fever was treated for possible peritonitis. There were no cases of other major complications, including gastric perforation, gastrocolic fistula, clinically significant bleeding, or PEG-related death documented. Conclusion: Consistent with previous studies, our data suggests a relationship between site complications (superficial wound infection, buried bumper syndrome) and neutropenia. Additionally, PEG placement appears to be an effective modality for improving nutritional status in malnourished pediatric oncology patients. However, larger prospective studies with appropriate controls and adjustment for potential confounders are warranted to confirm these findings.

• 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.

• Asian-Australasian Journal of Animal Sciences
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• v.7 no.1
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• pp.83-89
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• 1994

The effects of inorganic selenium (Se), selenate and selenite on Se balance levels in the different ruminal fluid fractions were studied using Japanese Corriedale wethers with an average body weight of 47 kg. A $3{\times}3$ Latin square design was used with three animal, three periods and three treatments. In each period, there was 7 d dietary adjustment followed by 5 d total collection of urine and feces. Ruminal fluid samples were obtained at 0, 1, 3, 5 and 7 h postprandially on the final day of the collection period. The three dietary treatments were: (1) without Se supplementation (control); (2) with Se supplement as sodium selenate; and (3) sodium selenite at a rate of 0.2 mg Se/kg dietary DM. The basal diet was timothy hay (Phleum pratense L.) fed 2% of body weight/d. Results indicated that Se balance were higher (p < 0.05) for those animals under supplementation than those animals under control. Overall data gathered showed a similar digestion balance of selenate and selenite in sheep. Inorganic Se, both selenate and selenite produced positive Se contents of the ruminal feed particles and protozoa. Bacterial Se increased (p < 0.05) on the first three hours post-prandially in Se supplemented diets. Gross ruminal fluid fraction, although there was improvement on their Se content under the supplemented diets, the changes were insignificant over the control. free inorganic Se and Se in soluble protein of the ruminal fluid were not significantly different for selenate and selenite. Most of the Se in the ruminal fluids of the animals under supplementation were insoluble, indicating the influence of rumen environments on Se bioavaliability.

• Journal of the Korean Applied Science and Technology
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• v.38 no.3
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• pp.762-770
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• 2021

The purpose of this study was to analyze the effect on the vertical ground reaction force, the elapsed time, and the center of pressure factors during gait by maepsi exercise program, which is a whole body exercise, to middle-aged women for 8 weeks. A total of 25 subjects participated in this study, 13 in the exercise group(age, 41±4.4 years; heigh, 162.5±5.8cm; weight, 57.8±6.7kg; body mass, 21.9±2.4kg/m2) and 12 in the control group(age, 41.1±5.6 years; height, 160.9±5.5 cm; weight, 576.2±8.1 kg; body mass, 21.7±2.9 kg/m2). In the exercise group, the maepsi exercise program consisting of 7 areas, 23 types and 77 movements, was conducted 3 times a week for 8 weeks. Two-way repeated measures ANOVA was performed to verify the ground reaction force factors during gait, and the post-test was analyzed with bonferroni adjustment(a=.05). In the exercise group, compared to the control group, the exercise group showed higher values than the control group in the elapsed time to FMWA and FPO, vertical ground reaction force at FMWA and FPO, and RMS factors of COP in the AP direction. Therefore, it was found that the 8-week maepsi exercise program improved the acceleration and deceleration exercise functions of middle-aged women who performed gait.