• Journal of the Korean Statistical Society
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• 제36권2호
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• pp.275-284
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• 2007

Confidence intervals for the population proportion in a double sampling scheme subject to false-positive misclassification are considered. The confidence intervals are obtained by applying Agresti and Coull's approach, so-called "adding two-failures and two successes". They are compared in terms of coverage probabilities and expected widths with the Wald interval and the confidence interval given by Boese et al. (2006). The latter one is a test-based confidence interval and is known to have good properties. It is shown that the Agresti and Coull's approach provides a relatively simple but effective confidence interval.

• Journal of the Korean Statistical Society
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• 제34권3호
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• pp.185-195
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• 2005

This article is concerned with the intraclass correlation in survey sampling. From a design-based viewpoint the intraclass correlation is generalized to a finite population with unequal sized clusters. Under simple random cluster sampling the intraclass correlation is given in an explicit form, which is a generalization of the usual one. The range of it is found and the design effect is expressed by means of it. An example is given to compare the intraclass correlation with the homogeneity measure numerically, which shows that two measures are not the same except some limited cases.

• 산업경영시스템학회지
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• 제13권21호
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• pp.81-90
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• 1990

In stratified random sampling a simple random sample must be taken in each stratum to reduce the maximum gain in precision given the minimum cost. The purpose of this paper is to deal with the propertics of the estimates and variances and obtain the economic design of stratified random sampling through the optimum allocation of the sample sizes. In addition, the between stratum variation and the within stratum variation is stratifying the population are described.

• 응용통계연구
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• 제28권6호
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• pp.1113-1120
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• 2015

본 논문에서는 사회적으로나 개인적으로 매우 민감한 조사에서 세대별, 연령별 또는 계층별에 따라 조사하고자 하는 모집단이 여러 개의 층으로 구성되어 있고, 각 층이 다지속성으로 되어 있는 경우에, Abul-Ela 등의 다지모형과 Eriksson의 다지무관모형에서 사용한 단순임의추출법 대신에 층화추출법을 적용하여 각 층의 다지속성에 대한 모비율의 추정뿐만 아니라 모집단 전체 모비율에 대한 추정을 할 수 있는 층화 다지 확률화응답모형을 제안하였다. 그리고 층화 다지모형에 있어서 각 층의 표본배분에 대하여 비례배분과 최적배분을 고려하여 다루었다. 또한 층화 다지 확률화응답모형들간의 효율성을 비교해 본 결과 Eriksson의 다지무관모형이 Abul-Ela 등의 다지모형보다 효율적임을 알 수 있었다.

• 통합자연과학논문집
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• 제9권1호
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• pp.67-71
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• 2016

The university president direct election system in Korea had begun in 1987 as a movement of college democratization in the 1980s after 6.29 Declaration. Since then, many national/private universities had adopted the election system. However, it has posed many problems and it caused a sharp division of opinions between those who approve and disapprove the direct election system. Since 2005, the government has made official of the reformation and/or abolition of the university president direct election system, and has kept pushing for universities to give up the direct election system. Now, only 3 or 4 universities hold on to the system, and many universities have changed into the indirect election system. In the indirect election, a key is the composition of president nomination committee, which confirms the university members's variety. Many universities adopting the indirect election system have used simple random sampling, like drawing lots, to compose the president nomination committee. However, drawing lots has a problem that it has large possibility of composing a biased committee. This research suggests systematic sampling as an alternative to drawing lots. A numerical analysis was conducted using a data of a university in which the indirect election was implemented recently. The drawing lots gave the biased nomination committee. On the other hand, the systematic sample improves the problem and confirms more the variety of all members.

• 한국대기환경학회지
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• 제30권4호
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• pp.362-377
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• 2014

Polycyclic aromatic hydrocarbons (PAHs) have been of particular concern since they are present both in the vapor and particulate phases in ambient air. In this study, a simple method was applied to determine the vapor phase PAHs, and the performance of the new method was evaluated with a conventional method. The simple method was based on adsorption sampling and thermal desorption with GC/MS analysis, which is generally applied to the determination of volatile organic compounds (VOCs) in the air. A combination of Carbotrap (300 mg) and Carbotrap-C (100 mg) sorbents was used as the adsorbent. Target compounds included two rings PAHs such as naphthalene, acenaphthylene, and acenaphthene. Among them, naphthalene was listed as one of the main HAPs together with a number of VOCs in petroleum refining industries in the USA. For comparison purposes, a method based on adsorption sampling and solvent extraction with GC/MS analysis was adopted, which is in principle same as the NIOSH 5515 method. The performance of the adsorption sampling and thermal desorption method was evaluated with respect to repeatabilities, detection limits, linearities, and storage stabilities for target compounds. The analytical repeatabilities of standard samples are all within 20%. Lower detection limits was estimated to be less than 0.1 ppbv. In the results from comparison studies between two methods for real air samples. Although the correlation coefficients were more than 0.9, a systematic difference between the two groups was revealed by the paired t-test (${\alpha}$=0.05). Concentrations of two-rings PAHs determined by adsorption and thermal desorption method consistently higher than those by solvent extraction method. The difference was caused by not only the poor sampling efficiencies of XAD-2 for target PAHs and but also sample losses during the solvent extraction and concentration procedure. This implies that the levels of lower molecular PAHs tend to be underestimated when determined by a conventional PAH method utilizing XAD-2 (and/or PUF) sampling and solvent extraction method. The adsorption sampling and thermal desorption with GC analysis is very simple, rapid, and reliable for lower-molecular weight PAHs. In addition, the method can be used for the measurement of VOCs in the air simultaneously. Therefore, we recommend that the determination of naphthalene, the most volatile PAH, will be better when it is measured by a VOC method instead of a conventional PAH method from a viewpoint of accuracy.

• Journal of the Korean Statistical Society
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• 제25권1호
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• pp.95-110
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• 1996

We consider the question of efficiency of the Bayes sequential procedure with respect to the optimal fixed sample size Bayes procedure in a simple vs. simple testing problem for data coming from a general nonregular density b(.theta.)h(x)l(x < .theta.). Efficiency is defined in two different ways in these caiculations. Also, the minimax sequential risk (and minimax sequential stratage) is studied as a function of the cost of sampling.

• 응용통계연구
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• 제25권3호
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• pp.447-456
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• 2012

For a sensitive survey in which the population is comprised of several clusters with a quantitative attribute, we present an additive quantitative randomized response model by cluster sampling that adapts a two-stage cluster sampling instead of a simple random sample based on Himmelfarb-Edgell's additive quantitative attribute model and Gjestvang-Singh's one. We also derive optimum values for the number of 1st stage clusters and the optimum values of observation units in a 2nd stage cluster under the condition of minimizing the variance given constant cost. We can see that Himmelfarb-Edgell's model is more efficient than Gjestvang-Singh's model under the condition of cluster sampling.

• 품질경영학회지
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• 제30권1호
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• pp.74-96
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• 2002

The objectives of this study is to suggest the rectifying sampling inspection plan considering quality cost. Limiting quality level(LQL) plans(also called LTPD plans) and outgoing quality(OQ) plans are considered. The Hald's linear cost model is discussed with and without a beta prior for the distribution of the fraction of nonconforming items in a lot. It is assumed that the sampling inspection is error free. We consider the design of reliability acceptance sampling plan (RASP) for failure rate level qualification at selected confidence level. The lifetime distribution of products is assumed to be exponential. MIL-STD-690C and K C 6032 standards provide this procedures. But these procedures have some questions to apply in the field. The cost of test and confidence level(1-$\beta$ risk) are the problem between supplier and user. So, we suggest that the optimal life test sampling inspection plans using simple linear cost model considering product cost, capability of environment chamber, environmental test cost, and etc. Especially, we consider a reliability of lots that contain some nonconforming items. In this case we assumed that a nonconforming item fail after environmental life test. Finally, we develope the algorithm of the optimal sampling inspection plan based on minimum costs for rectifying inspection and RASP. And computer application programs are developed So, it is shown how the desired sampling plan can be easily found.

• 한국정보통신학회논문지
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• 제15권8호
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• pp.1805-1812
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• 2011

Bandpass sampling(BPS) 기술은 나이퀴스트(Nyquist) 샘플링 주파수보다 낮은 주파수를 사용하여 RF 대역의 신호를 직접 하향변환 할 수 있다는 장점을 가지고 있지만, 나이퀴스트 영역에서 self-image의 중복을 피하기 위해서는 샘플링 주파수의 선택에 제약이 따른다. 2개의 ADC를 사용하는 2차(second-order) BPS는 self-image를 제거하기 위한 신호처리가 추가 된다는 조건으로 샘플링 주파수의 선택이 자유롭다. 하지만 RF 대역이 바뀌면 신호처리를 위한 파라미타를 재구성해야 한다. 본 논문에서는 2차 BPS의 한 형태인 quadrature BPS의 구조를 가지면서, 재구성이 필요 없는 간단한 보상 필터만을 사용하여 임의 RF 대역으로부터 나이퀴스트 영역으로 하향 변환하는 complex BPS 기반의 SDR front-end에 대하여 기술한다.