• 응용통계연구
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• 제7권2호
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• pp.269-277
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• 1994

최소카이제곱추정에 의하여 구한 추정량의 표본분포를 붓스트랩으로 근사시켰을 때에도 정규근사와 최소한 동등함을 설명하고, 이 이론을 자궁경부암 조직에서 검출되는 란게르한스 세포의 출현률 추정에 이용하였다. 란게르한스 세포의 출현횟수를 포지티브 포아송 모형에 적합시켰으며, 추정된 출현률의 표준오차는 대표본 근사 및 붓스트랩을 이용하여 계산하였다. 두 방법 모두 비슷한 결과를 제공하였다.

• Journal of the Korean Statistical Society
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• 제12권1호
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• pp.24-35
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• 1983

In fitting models to data, selection of the most desirable estimation method and determination of the adequacy of fitted model are the central issues. This paper compares the maximum likelihood estimators and the minimum logit chi-square estimators, both being best asymptotically normal, when logit models are fitted to infant mortality data. Chi-square goodness-of-fit test and likelihood ratio one are also compared. The analysis infant mortality data shows that the outlying observations do not necessarily result in the same impact on goodness-of-fit measures.

• International Journal of Reliability and Applications
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• 제14권1호
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• pp.27-39
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• 2013

In this article, a new model based on the Rayleigh distribution is introduced. This model is useful and practical in physics, reliability, and life testing. The statistical and reliability properties of this model are presented, including moments, the hazard rate, the reversed hazard rate, and mean residual life functions, among others. In addition, it is shown that the distributions of the new model are ordered regarding the strongest likelihood ratio ordering. Four estimating methods, namely, method of moment, maximum likelihood method, Bayes estimation, and uniformly minimum variance unbiased, are used to estimate the parameters of this model. Simulation is used to calculate the estimates and to study their properties. Finally, the appropriateness of this model for real data sets is shown by using the chi-square goodness of fit test and the Kolmogorov-Smirnov statistic.

• Journal of the Korean Statistical Society
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• 제30권1호
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• pp.1-20
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• 2001

We present how bootstrap methods can be used to conduct inference on the rates of Poisson distributions when only the grouped data are available. A theoretical justification for the validity of bootstrap is given with an illustration of proposed method using a data set obtained fro ma pathology laboratory test. Traditional asymptotic methods are compared with bootstrap methods in computing the estimated standard errors and achieved significance levels for one sample and two sample tests. Bootstrap methods are shown to possess a nice property that he small sample distribution of the relevant statistics can be readily obtained from the bootstrap copies.

• 전자공학회논문지A
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• 제30A권8호
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• pp.11-18
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• 1993

In a spread spectrum system, the bandwidth and period of spreading code is wide and long, respectively. So it is necessary to make the code acquisition time as short as possible. In particular, serial search code acquisition system requires optimum dwell time for fast acquisition. In this paper, code acquisition time is calculated by varying dwell time. Among them, minimum code acquisition time is chosen and then optimum dwell time can be obtained. Detection probability (P$_{D}$) and false alarm probability (P$_{FA}$) can be obtained by integrating chi-square pdf by numerical analysis. The results are compared with that of gaussian approximation method and then it is concluded gaussian approximation method is not suitable for obtaining optimum dwell time. Computer simulation supports theoretical results.

• Journal of Korean Dental Science
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• 제16권1호
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• pp.63-73
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• 2023

Purpose: Hyperdontia is a developmental disorder of the oral cavity. Mesiodens refers to the hyperdontia located between the maxillary central incisors. During the surgical procedure, the anesthetic method for pain control should be considered along with factors related to the surgery itself. The purpose of this study was to evaluate the effect of the impacted position of the mesiodens on the selection of sedation method and to suggest incisive foramen as a brief reference. Materials and Methods: This study included 126 patients who were scheduled for extraction of mesiodens. The selection criteria included patients with one palatally impacted inverted mesiodens accessible from the palatal gingival margin, and those with good cooperation potential in order to control for clinical information. Using cone beam computed tomography, vertical, horizontal, and palatal positional factors were measured, and the anesthetic method was determined by two examiners. The patients were grouped into vertical and horizontal groups based on the position of the incisive foramen. Data were statistically analyzed using the Mann-Whitney test, the chi-square test, and logistic regression analysis. Result: All positional factors differed between the outpatient and inpatient anesthetic groups. The vertical minimum distance from the alveolar ridge to the mesiodens (Va) and the minimum distance from the palatal surface to the crown tip of the mesiodens (Tc) were factors affecting the choice of anesthetic method. The distribution of the vertical and horizontal positional groups differed between the outpatient and inpatient anesthetic groups. Conclusion: The incisive foramen can be used as a brief reference to determine the appropriate anesthetic method. Referral for inpatient anesthesia may be a priority if they are in the V₂H₂ group with Va ≥5 mm, and Tc ≥6 mm, and outpatient sedation may be considered if they are in the V₁H₁ group with Va ≤1.5 mm, and Tc ≤2.5 mm.

• Nutrition Research and Practice
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• 제12권6호
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• pp.512-520
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• 2018

BACKGROUND/OBJECTIVES: The 6-23 months for infants is the longest period in the "first 1,000 days" of life. This period is very important for child development, so complementary feeding (CF) practices should be optimized to maximize children's potential for growth and development. The aim of this study was to analyze the CF practices and nutritional status of children aged 6-23 months. SUBJECTS/METHODS: For this cross-sectional study, 392 children aged 6-23 months were selected using stratified random sampling. Socio-demographic data were collected through interviews. CF practices, collected by interviews and repeated 24-hour food recall method, were the timely introduction of CF, minimum meal frequency, dietary diversity and minimum acceptable diet, consumption food rich in proteins and vitamin A. Nutritional status was assessed using the indicators of underweight, wasting and stunting. To analyze the association between socio-demographic indicators and CF with nutritional status, the chi-square test with a confidence interval of 95% was used. RESULTS: Results showed that 39% were exclusively breastfed, only 61% received prolonged breastfeeding and 50% received timely introduction of CF. Minimum meal frequency was met by 74% of subjects, but dietary diversity and minimum acceptable diet were only realized in 50% and 40% of the children, respectively. The prevalence of underweight, wasting, and stunting were 26%, 23%, and 28%, respectively. Age of the child, birth order, birth weight, parents' education level, family size and incidence of fever and diarrhea during the previous two weeks were associated with underweight, while child's birth order, fathers' education level, mother's age, family size, completion of the age-appropriate vaccination and fish consumption frequency were associated with wasting. Age of the child, incidence of fever and acute respiratory infection, and fortified food consumption were associated with stunting. CONCLUSIONS: Suboptimal CF practices and high prevalence of underweight, wasting and stunting were found among children aged 6-23 months old in Aceh. These results highlight the need to improve CF and nutritional status.

• 대한한의학회지
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• 제33권4호
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• pp.1-8
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• 2012

Objectives: The purpose of this study was to specify major tongue diagnostic indicators and evaluate their significance in discriminating pattern identification subtypes in stroke patients. Methods: This study used a community based multi-center observational design. Participants (n=1,502) were stroke patients admitted to 11 oriental medical university hospitals between December 2006 and February 2010. To determine which tongue indicator affected each pattern identification, a decision tree analysis of the chi-square automatic interaction detector (CHAID) algorithm was performed. The chi-squared test was used as the criterion in splitting data with a p-value less than 0.05 for division, which is the main procedure for developing a decision tree. The minimum sample size for each node was specified as n =10, and branching was limited to two levels. Results: From the 9 tongue diagnostic indicators, 6 major tongue indicators (red tongue, pale tongue, yellow fur, white fur, thick fur, and teeth-marked tongue) were identified through the decision tree analysis. Furthermore, each pattern identification was composed of specific combinations of the 6 major tongue indicators. Conclusions: This study suggests that the 6 tongue indicators identified through the decision tree analysis can be used to discriminate pattern identification subtypes in stroke patients. However, it is still necessary to re-evaluate other pattern identification indicators to further the objectivity and reliability of traditional Korean medicine.

• 유통과학연구
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• 제13권9호
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• pp.103-112
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• 2015

Purpose - This paper aims to provide a step-by-step approach to factor analytic procedures, such as principal component analysis (PCA) and exploratory factor analysis (EFA), and to offer a guideline for factor analysis. Authors have argued that the results of PCA and EFA are substantially similar. Additionally, they assert that PCA is a more appropriate technique for factor analysis because PCA produces easily interpreted results that are likely to be the basis of better decisions. For these reasons, many researchers have used PCA as a technique instead of EFA. However, these techniques are clearly different. PCA should be used for data reduction. On the other hand, EFA has been tailored to identify any underlying factor structure, a set of measured variables that cause the manifest variables to covary. Thus, it is needed for a guideline and for procedures to use in factor analysis. To date, however, these two techniques have been indiscriminately misused. Research design, data, and methodology - This research conducted a literature review. For this, we summarized the meaningful and consistent arguments and drew up guidelines and suggested procedures for rigorous EFA. Results - PCA can be used instead of common factor analysis when all measured variables have high communality. However, common factor analysis is recommended for EFA. First, researchers should evaluate the sample size and check for sampling adequacy before conducting factor analysis. If these conditions are not satisfied, then the next steps cannot be followed. Sample size must be at least 100 with communality above 0.5 and a minimum subject to item ratio of at least 5:1, with a minimum of five items in EFA. Next, Bartlett's sphericity test and the Kaiser-Mayer-Olkin (KMO) measure should be assessed for sampling adequacy. The chi-square value for Bartlett's test should be significant. In addition, a KMO of more than 0.8 is recommended. The next step is to conduct a factor analysis. The analysis is composed of three stages. The first stage determines a rotation technique. Generally, ML or PAF will suggest to researchers the best results. Selection of one of the two techniques heavily hinges on data normality. ML requires normally distributed data; on the other hand, PAF does not. The second step is associated with determining the number of factors to retain in the EFA. The best way to determine the number of factors to retain is to apply three methods including eigenvalues greater than 1.0, the scree plot test, and the variance extracted. The last step is to select one of two rotation methods: orthogonal or oblique. If the research suggests some variables that are correlated to each other, then the oblique method should be selected for factor rotation because the method assumes all factors are correlated in the research. If not, the orthogonal method is possible for factor rotation. Conclusions - Recommendations are offered for the best factor analytic practice for empirical research.

• 콘크리트학회논문집
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• 제16권6호
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• pp.833-840
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• 2004

비파괴 검사에 의한 콘크리트 압축강도 시험법 중에서 반발도법과 초음파 속도법은 가장 널리 사용되는 방법이다. 그러나 국내에서 사용되고 있는 비파괴 강도 시험법은 대부분이 외국의 시험법을 적용하고 있어서 국내의 콘크리트 구조물에 직접 적용하는 데는 무리가 따른다고 할 수 있다. 반발도법의 경우, 일본건축학회 등의 제안에 자라 20개의 타격점을 표준으로 채택하고 있으나 표준편차에 대한 고려를 하지 않고 있는 실정이다. 또한, 초음파 속도법에 의한 시험은 압축강도를 추정하는데 필요한 측정횟수의 규정이 없다 따라서 본 연구에서는 카이검증을 이용하여 비파괴 검사법에 의한 콘크리트 압축강도의 타격횟수의 신뢰도를 검토하고 최소시험 횟수를 제안하였다. 그 결과, 반발도법과 초음파 속도법으로 추정한 콘크리트 압축강도 값이 만족할 만한 신뢰범위에 들기 위한 최소시험횟수는 각각 11회와 7회로 분석되었다. 다만, 실구조물의 품질변동을 고려하여 이상치의 결측처리와 시험군의 격자 배열을 전제로 한다면, 반발도법은 국내의 관행에 따라 20회로, 음파 속도법은 9회로 규정하는 것이 바람직하다고 판단된다.