• Communications for Statistical Applications and Methods
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• 제6권1호
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• pp.193-205
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• 1999

An approximate Bayes criterion for Behrens-Fisher problem (testing equality of means of two normal populations with unequal variances) is proposed and examined. Development of the criterion involves derivation of approximate Bayes factor using the imaginary training sample approachintroduced by Spiegelhalter and Smith (1982). The proposed criterion is designed to develop a Bayesian test criterion having a closed form, so that it provides an alternative test to those based upon asymptotic sampling theory (such as Welch's t test). For the suggested Bayes criterion, numerical study gives comparisons with a couple of asymptotic classical test criteria.

• 재무관리연구
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• 제26권2호
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• pp.181-201
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• 2009

This study is on the forecasting performance analysis of range volatility estimators(Parkinson, Garman and Klass, and Rogers and Satchell) relative to historical one using two-scale realized volatility estimator as a benchmark. American sub-prime mortgage loan shock to Korean stock markets happened in sample period(January 2, 2006~March 10, 2008), so the structural change somewhere within this period can make a huge influence on the results. Therefore sample was divided into two sub-samples by May 30, 2007 according to Zivot and Andrews unit root test results. As expected, the second sub-sample was much more volatile than the first sub-sample. As a result of forecasting performance analysis, Rogers and Satchell volatility estimator showed the best forecasting performance in the full sample and relatively better forecasting performance than other estimators in sub-samples. Range volatility estimators showed better forecasting performance than historical volatility estimator during the period before the outbreak of structural change(the first sub-sample). On the contrary, the forecasting performance of range volatility estimators couldn't beat that of historical volatility estimator during the period after this event(the second sub-sample). The main culprit of this result seems to be the increment of range volatility caused by that of intraday volatility after structural change.

• 한국환경과학회지
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• 제20권4호
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• pp.493-500
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• 2011

This study investigates the relationship between Asian dust and asthma disease in Seoul, using data of Asian dust occurrences and the number of treatments for asthma between 2005 and 2008. The data include the number of treatments for asthma on the basic day paired with the average number of treatments for asthma on the compared days. The compared day is defined by the day of no Asian dust in same month and day of the week as the basic day, when Asian dust occurs. Also, the basic day is expanded to the day after three days from the day of Asian dust. The paired two sample t-test for the number of treatments for asthma on the basic day and the compared days revealed that the Asian dust occurrences are correlated with the asthma disease. The number of treatments for asthma is significantly increased on the one and two days after Asian dust occurs. On the other hand, there's no significant difference in the number of treatments for asthma between the days of Asian dust occurrence and the days of no Asian dust, which implies that people usually try not to go out when Asian dust occurs.

• 대한임상검사과학회지
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• 제37권3호
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• pp.220-227
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• 2005

Recently, the use of an electrical apparatus has brought up concerns of health risks from exposure to electromagnetic fields. EMF is composed of electric fields and magnetic fields. Heavy exposure to EMF can occur only in the vicinity of high-voltage overhead transmission lines, close to transformers and underground cables, and also close to large electrical machinery. In this thesis I have investigated the hypothesis of the correlation between occupational exposure to ELF-EMF and the risks of leukemia, anemia, cancer. Therefore, the aim of this study is to investigate whether or not ELF-EMF emitted from electric power stations and transformer substations affect some hematological parameters and tumor markers of electric utility workers. The hematological test results and tumor markers under investigation were similar in the two groups but some of parameters such as RBC, AFP, LDH showed significant difference between the two groups from two sample t-test (p<0.05). The exposure group showed increased LDH level compared to the control group by two sample t-tests. In addition, the abnormal LDH level in the exposure group was observed to be clinically significant by ${\chi}^2$-test. However, the levels of RBC, AFP observed were not clinically significant by ${\chi}^2$-test (p>0.05). These results suggested that ELF-EMF does not affect most blood test parameters except LDH of electric utility workers.

• Communications for Statistical Applications and Methods
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• 제6권3호
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• pp.893-900
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• 1999

We use statistical tests which are useful for two-sample problem for detecting edges in gray-level images. An edge is detected by examining changes in gray-level value between adjacent pixel neighborhoods. Some experimental results show that nonparametric detectors such as Mann-Whitney test median test and Kolmogorov-Smirnov test perform effectively in both noisy and noise-free images while parametric T test is sensitive to noise.

• 한국잠사곤충학회지
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• 제13권1호
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• pp.69-72
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• 1971

1. 연감시료량의 적정량을 알아보기 위해 200, 100, 50, 20, 10gr의 생사시료를 연감검사한 결과 각처리간에는 통계적차이를 인정할 수 없었으나 실제로 시료량의 과대 과소에 따른 측정 및 처리오차를 감안할 때 100gr 시료가 적정량이었다. 2. 섬도사를 이용하여 연감검사를 할 경우 꼬인 상태와 풀은 상태로 연감처리할 경우 탄산나트륨같이 제교력이 강한 정연제에서는 차이가 없었으나 Marseilles 비누같이 제교력이 약한 것은 연감율에 있서 현저한 차이가 있었다. 3. 5종의 정연제를 비교한 결과 합성세제와 국산 Marseilles비누와 통계적 유의차를 인정 할 수 없으므로 이와의 대체 이용이 가능하다. 4. 정연제의 제교력은 대체로 정연액의 PH가 클수록 크고 작을수록 작은 경향이 있다.

• 패션비즈니스
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• 제19권6호
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• pp.14-27
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• 2015

This study explores the comparison of body image, body satisfaction, and clothing behaviors between Korean and British young women. Body image was measured by two methods: visual and verbal. For the data analysis, the Statistical Package for Social Science (SPSS) Version 16.0 for Windows was used to provide descriptive statistics, an independent sample t-test, and paired sample t- tests were applied in this study. Our results show that Korean and British female college students perceived ideal-body images that were smaller than their self defined body images. The ideal and self-images were significantly different in both groups. Both groups were dissatisfied with their own body size. The study was limited to a small sample size. Future studies using more participants from a more diverse age group and ethnic groups are recommended. The study will help marketers and retailers develop new products and new markets aimed at Korean and British women related to body image and body satisfaction.

• Journal of the Korean Data and Information Science Society
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• 제23권4호
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• pp.787-796
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• 2012

본 연구의 목적은 PAPS를 실시하여 4, 5급에 해당하는 저체력군 학생을 대상으로 16주 복합운동프로그램을 통해 대사증후군과 자율신경계에 어떠한 변화가 나타나는가를 규명하는 것이다. 16주 복합운동프로그램은 주 5회에 걸쳐 준비운동, 본운동, 정리운동으로 구성하고 1회 50분씩 실시하였다. 자료처리는 SPSS 19.0 통계프로그램을 이용하여 모든 종속변인들의 평균과 표준편차를 산출하였다. 샤피로-윌크 검정값을 이용하여 정규성 검정을 실시하였고, 복합운동집단과 통제집단의 모평균 차이를 위하여 독립표본 t-검정을 실시하였으며, 16주 복합운동프로그램 전 후 각 집단 내변인들의 변화를 알아보기 위해 대응표본 t-검정을 실시하였다. 모든 통계치의 유의수준은 ${\alpha}$=.05로 처리하여 다음과 같은 결과를 얻었다. 본 연구 결과 대사증후군 지표에서는 허리둘레, 중성지방, 공복혈당, HDL-C에서 유의한 차이를 나타냈고, 자율신경계 요인에서는 통계적으로 모두 유의한 차이가 나타나 저체력군 고등학생에 긍정적인 영향을 미친 것으로 사료되어 진다.

• Communications for Statistical Applications and Methods
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• 제9권3호
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• pp.877-887
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• 2002

In this paper, behaviors and properties of p-values for goodness-of-fit test are investigated. With some findings on the p-values, we consider some applications to determine sample size of a survey research using the regression equation based on a pilot study data. Regression equations are obtained by the well-known least squared method, and we find that regression lines could be formulated with only two data points, alternatively. For further studies, this works might be extended to t distributions for testing hypotheses about population mean in order to determine sample size of a prospective study. Also similar arguments could be explored for F test statistics.

• 대한치과기공학회지
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• 제44권4호
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• pp.126-131
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• 2022

Purpose: The purpose of this study is to evaluate the quality of dental fixed prostheses fabricated by 3DP (three-dimensional printing). Methods: Ten main models were prepared for the study. Ten specimens were printed by 3DP (3DP group). Ten specimens were fabricated by the lost wax technique and casting method to complete the control group (LWC group). The marginal fit was measured for 20 specimens. The measurement of marginal fit was performed using the silicon replica technique. Finally, the marginal fit of 10 specimens from each group was calculated. An independent sample t-test was run to see if the calculated averages for the two groups were mutually significant (α=0.05). Results: According to the experimental results, the mean marginal fit of the 3DP group was 71.9 ㎛, and the LWC group was 55.3 ㎛. The means of the two groups were found to be significantly different (p<0.001) in the results of the independent sample t-test. Conclusion: The marginal fit of fixed dental prostheses produced by 3DP technology was examined with values greater than those fabricated by traditional technology. However, as it appeared to be a value within the range of clinically acceptable range recommended by numerous studies, it was determined that clinical application would be feasible.