• The Korean Journal of Applied Statistics
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• v.8 no.2
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• pp.109-119
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• 1995

A two sample chi-square test is introduced for testing the equality of the distributions of two populations when observations are subject to random censorship. The statistic is appropriate in testing problems where a two-sided alternative is of interest. Under the null hypothesis, the asymptotic distribution of the statistic is a chi-square distribution. We obtain two types of chi-square statistics ; one as a nonnegative definite quadratic form in difference of observed cell probabilities based on the product-limit estimators, the other one as a summation form. Data pertaining to a cancer chemotheray experiment are examined with these statistics.

• Communications for Statistical Applications and Methods
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• v.2 no.2
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• pp.249-265
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• 1995

본 논문에서는 확률분포가 알려져 있지 않은 두 모집단 중 어느 하나로 새로운 관측치를 분류할 때 오분류확률이 분석자에 의해 사전에 정해진 수준에 부합할 수 있도록 커널 판별함수의 임계치를 결정하였다. 정해진 오분류확률을 만족시키기 위한 판별함수의 임계치는 붓스트랩(bootstrap)기법을 판별 함수에 적용시켜 계산된다. 본 논문에서 제시도된 방법은 모집단에 대한 모수적 가정이 없으므로 어느 분포에도 적용가능하며, 모집단이 정규분포, 대수정규분포, 이산형과 연속형 변수가 혼합된 분포의 경우 모의실험을 통하여 그 성능에 대한 검증을 하였다.

• The Korean Journal of Applied Statistics
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• v.21 no.1
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• pp.177-182
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• 2008

There are times when we need more sample to achieve a more accurate estimator. Since these two sets of sample have the information about the same population, it is necessary to treat both as a single combined data. In this paper we present the unpooled sample variance for the combined data when we just know a sample mean and variance for the each data set without the raw data. It is shown that the pooled variance $s^2_p$ is always greater than the exact variance $s^2_t$ when ${\bar{x}}_n\;=\;{\bar{y}}_m$. And the difference of means for two data, ${\bar{x}}_n-{\bar{y}}_m}$, is larger, the difference of $s^2_p$ and $s^2_t$ is larger.

• The Korean Journal of Applied Statistics
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• v.30 no.5
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• pp.691-699
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• 2017

Data analysts sometimes test the equality of two normal population means by the inspection of the overlapping of two confidence intervals. This method seems simple to use; however, it is a common statistical misconception to suppose that two normal means are not significantly different because of no overlapping. This article will present transforming the confidence interval of the mean difference to individual confidence intervals that are visualized to inspect overlapping. It will also be shown that this technique can be extended when comparing the k normal population means with equal variances.

• Proceedings of the Korea Water Resources Association Conference
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• 2009.05a
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• pp.1157-1161
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• 2009

본 연구에서는 부트스트랩(Bootstrap) 기법을 이용하여 측우기 강우량 관측계열(CWK)과 근대우량계 강우량 관측계열(MRG)에 대해 동질성 분석을 실시하였다. 서로다른 두 자료계열에 대한 전통적인 통계적 동질성 검정 방법은 모집단의 분포형을 알고 있어야 검정결과가 유효하였기 때문에 모집단의 분포가 복잡한 기상자료들은 이러한 전통적 방법을 사용하여 동질성을 파악하는 것이 매우 어려웠고 결과로 제시된 통계적 유의성에 대해서도 의심의 여지가 있었다. 이러한 이유로 본 논문에서는 모집단을 가정하지 않아도 되는 비모수적 모의 방법인 부트스트랩 기법을 이용하여 두 자료계열간의 동질성 검정을 실시하였다. 분석 결과 M20의 CWK와 MRG는 미소한 기후의 경년변화 (Trend)의 영향을 제외하면 동질성을 가진 자료로 볼 수 있었으나, 갈수기의 경우는 월강우량의 크기에 변화가 있으며 호우기의 경우는 일강우량의 크기 및 호우의 형태에 변화가 있는 것으로 나타났다.

• Journal of Korea Water Resources Association
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• v.42 no.10
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• pp.795-807
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• 2009

In this study, homogeneity analysis was performed between rainfall observation data set of Chukwooki (CWK) and rainfall observation data set of modern rain gage (MRG) using Bootstrap method. Since traditional statistical homogeneity test method are validated only when distribution of their population is known, meteorological data which their statistical distributions of population are complicated were difficult to verify the homogeneity and there were plenty of room for doubt for their statistical significance using historical method. In this reason, in this study homogeneity test was evaluated between two data sets using bootstrap method which is not necessary to infer distribution of population. The test results show that there was an statistical homogeneity between CWK and MRG except for slight impact of climatical trend.

• Journal of the Korean Data and Information Science Society
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• v.20 no.6
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• pp.1103-1118
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• 2009

When we wish to estimate the mean or total of a finite population, the numbering of the population units is of importance. In this paper, we have proposed two methods for estimating the mean or total of a population having a linear trend, for the case when the reciprocal of the sampling fraction is an even number and the sample size is an odd number. The first method involves drawing a sample by using a method which is a generalization of Singh et al's (1968) modified systematic sampling, and using interpolation in determining the estimator. The second method involves selecting a sample by modified systematic sampling, and estimating the population parameters by the regression estimation method. Under the criterion of the expected mean square error based on Cochran's (1946) infinite superpopulation model, the proposed methods have been compared with existing methods. We have also made a comparison between the two proposed methods.

• Journal of Internet Computing and Services
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• v.14 no.5
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• pp.49-57
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• 2013

A novel approach for the feature selection is proposed, which is the important preprocessing task of on-line document classification. In previous researches, the features based on information from their single population for feature selection task have been selected. In this paper, a mixed feature set is constructed by selecting features from multi-population as well as single population based on various information. The mixed feature set consists of two feature sets: the original feature set that is made up of words on documents and the transformed feature set that is made up of features generated by LSA. The hybrid feature selection method using both filter and wrapper method is used to obtain optimal features set from the mixed feature set. We performed classification experiments using the obtained optimal feature sets. As a result of the experiments, our expectation that our approach makes better performance of classification is verified, which is over 90% accuracy. In particular, it is confirmed that our approach has over 90% recall and precision that have a low deviation between categories.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.40 no.2
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• pp.11-19
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• 2003

This paper proposes an algorithm to reduce the estimation error of surface spectral-reflectance(SR) using a conventional 3-band RGB camera. In the proposed method, estimation error can be reduced by using adaptive principal components(PCs) for each color region. In order to build adaptive set of PCs, n SR populations are organized for n PC sets by using Lloyd quantizer design algorithm. Macbetch ColorCheckcer is utilized as initial representative SR values for 1485 Munsell color chips of total color population and the Munsell chips arc divided subsets and a set of corresponding adaptive PCs per each subset is organized. As a result of experiments, the proposed method showed advanced estimation performance compared to both the two 3-band PCA methods and the 5-band wiener method.

• Journal of KIISE:Software and Applications
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• v.34 no.11
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• pp.971-983
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• 2007

Cellular Genetic Algorithms(CGAs) are a subclass of Genetic Algorithms(GAs) in which each individuals are placed in a given geographical distribution. In general, CGAs# population space is a regular network that has relatively long characteristic path length and high clustering coefficient in the view of the Networks Theory. Long average path length makes the genetic interaction of remote nodes slow. If we have the population#s path length shorter with keeping the high clustering coefficient value, CGAs# population space will converge faster without loss of diversity. In this paper, we propose Smallest-Small-World Cellular Genetic Algorithms(SSWCGAs). In SSWCGAs, each individual lives in a population space that is highly clustered but having shorter characteristic path length, so that the SSWCGAs promote exploration of the search space with no loss of exploitation tendency that comes from being clustered. Some experiments along with four real variable functions and two GA-hard problems show that the SSWCGAs are more effective than SGAs and CGAs.