• Communications for Statistical Applications and Methods
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• 제19권1호
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• pp.23-32
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• 2012

본 논문은 유한모집단에서 회귀계수추정량의 근사편향과 근사분산을 다루고 있다. 유한모집단에서 고정크기 포함확률비례표본을 추출하고 이 표본에서 조사된 데이터에 기초하여 회귀계수를 일반최소제곱추정량과 가중최소제곱추정량으로 추정할 때 두 추정량의 편향, 분산 그리고 평균제곱오차의 근사식을 유도하였다. 그리고 두 추정량의 효율을 비교하기 위하여 두 추정량의 분산을 비교하는 필요충분조건을 제시하였다. 또한 수치적인 비교를 위하여 간단한 예제를 소개하였다.

• 한국임상수의학회지
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• 제29권1호
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• pp.58-62
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• 2012

To protect aquatic animal health of importing countries from the potential risks associated with exotic diseases introduced through international trade of live aquatic animals, inspection of designated commodities at ports of entry is a critical component of the safeguarding system. The only way to be 100% confident that no fishes in a shipment are infected with a specific agent is to test every fish in the commodity imported with a perfect diagnostic test. For the majority of cases, this is unrealistic since the group of interest may very large particularly for aquatic animals, or imperfect tests are often available. It is, therefore, more common to test a fixed proportion of a group by preplanned sampling schemes. However, decision making based on results of testing the sample can provide quite a chance that infected groups may be misclassified as uninfected, depending on sampling strategy employed. The objective of this study was to determine the possibility that one or more fishes in the group imported being infected but tests negative after inspecting samples. This question is critical to government authorities to examine whether sampling plan is sufficient to achieve the purpose intended for. At fixed population size, the maximum number of infected fishes when all tests negative was decreased as the sampling fraction increased. The probability of including at least one undetected but infected fish in a group for negative tests increased with the number of fish tested or true prevalence. The risk was much lesser where high sensitivity test was assumed; when increasing test sensitivity from 0.9 to 0.99, this risk was dramatically reduced to about a tenth or a fourth for prevalence ranges from 2 to 10%, given sample size ranges from 10 to 200. Based on the preliminary analysis, the author concluded that current sampling plan testing 4-8% of the import proposal for human consumption still can yield high false negative results. Therefore, from the quarantine inspection point of view, an enforced commodity-specific sampling design that accounts for the cost of testing with an imperfect test at the specified design prevalence is urgent.

• 응용통계연구
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• 제10권2호
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• pp.339-352
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• 1997

소표본으로부터 형성되는 2원 분할표에는 빈도가 작은 칸들이 적지 않기 때문에 대표본이론에 근거한 카이제곱 검증 등 기존 통계적 방법의 적용이 적절하지 않응 수가 있다. 이런 경우에 한 대안으로서 정확검증법(exact tests)이 개발되어 있으나 이것이 너무 많은 계산을 요구하므로 사용하기가 쉽지 않다. 본 연구는 소표본 2원 분할표에서, 단순한 몬테칼로 알로리즘에 의한 행 균일성 가설의 카이제곱 임의화 검증법(randomization test)을 제안하고 튜키(Tukey) 형의 행간 다중비교법을 제안한다. 아울러 열 범주가 순서형인 2원 분할표에 대하여도 유사한 방법론을 적용할 수 있음을 밝힌다.

• 품질경영학회지
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• 제33권4호
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• pp.117-122
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• 2005

Variable sampling rate(VSR) scheme varies the sampling rate for the current sample depending on the previous value of the control statistic. In this paper, we propose EWMA control charts with variable parameter(VP) scheme, which allows both the sample rate(the sample size or the sampling interval) and the weight to vary. We investigate the effectiveness of the VP scheme relative to the fixed parameter(FP) scheme and the VSR scheme in EWMA control charts. It is shown that using the VP scheme gives some improvements to the ability in detecting small and moderate shifts in the process normal mean.

• 품질경영학회지
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• 제22권2호
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• pp.89-97
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• 1994

We consider the linear calibration model: $y_1={\alpha}+{\beta}x_i+{\sigma}{\varepsilon}_i$, i = 1, ${\cdots}$, n, $y={\alpha}+{\beta}x+{\sigma}{\varepsilon}$ where ($y_1$, ${\cdots}$, $y_n$, y) stands for an observation vector, {$x_i$} fixed design vector, (${\alpha}$, ${\beta}$) vector of regression parameters, x unknown true value of interest and {${\varepsilon}_i$}, ${\varepsilon}$ are mutually uncorrelated measurement errors with zero mean and unit variance but otherwise unknown distributions. On the basis of simple small-sample low-noise approximation, we introduce a new method of comparing the mean squared errors of the various competing estimators of the true value x for finite sample size n. Then we show that a class of estimators including the classical and the inverse estimators are consistent and first-order efficient within the class of all regular consistent estimators irrespective of type of measurement errors.

• Journal of the Korean Statistical Society
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• 제33권3호
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• pp.339-351
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• 2004

In this paper we generalize and improve the refined Pickands estimator of Drees (1995) for the extreme value index. The finite-sample performance of the refined Pickands estimator is not good particularly when the sample size n is small. For each fixed k = 1,2,..., a new estimator is defined by a convex combination of k different generalized Pickands estimators and its asymptotic normality is established. Optimal weights defining the estimator are also determined to minimize the asymptotic variance of the estimator. Finally, letting k depend upon n, we see that the resulting estimator has a better finite-sample behavior as well as a better asymptotic efficiency than the refined Pickands estimator.

• 한국수학교육학회지시리즈B:순수및응용수학
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• 제4권1호
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• pp.97-104
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• 1997

The large deviations theorem of Cramer is extended to conditional probabilities in the following sense. Consider a random sample of pairs of random vectors and the sample means of each of the pairs. The probability that the first falls outside a certain convex set given that the second is fixed is shown to decrease with the sample size at an exponential rate which depends on the Kullback-Leibler distance between two distributions in an associated exponential familiy of distributions. Examples are given which include a method of computing the Bahadur exact slope for tests of certain composite hypotheses in exponential families.

• 산업기술연구
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• 제23권A호
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• pp.21-27
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• 2003

The bio-micro pin is usually used for biochemistry analysis. The capability of manufacturing the micro-pin and array with effective and low-cost way is very important to developers. The micro-pin is composed of "sample channel" putting liquid into already fixed volume, "flat tip" having connection with printing quantity, and "head part" for preventing it from rotation of pin in the holder. We analyzed out printing variation in accordance with shape and tip size of the micro-pin point channel, In this study, we suggested the manufacturing progress and shape demand condition of the micro-pin which could put $0.2{\mu}{\ell}$-biochemistry material into the sample volume, and will be able to produce the micro-pin which can put $10n{\ell}$-biochemistry material into the sample volume in the future.

• 응용통계연구
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• 제14권1호
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• pp.13-24
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• 2001

이중추출에서 모평균 추정방법을 고찰하였다. 전통적으로 널리 쓰이는 비추정량과 회귀추정량 그리고 비례배분 및 Rao 배분을 한 후의 층화평균에 대하여 주어진 기대 비용에서 최적의 표본수, 최소분산 및 분산추정량을 살펴보았다. 또한 비추정 및 층화의 효과를 모두 내포하는 결합비 추정량을 제안하고 주어진 기대 비용에서 최적의 표본수 및 최소분산을 유도하였고 분산추정량을 구하였다. 그리고 제한된 모의실험을 통하여 비추정량, 층화평균 및 결합비 추정량의 효율을 비교하였다. 모의실험 결과 비추정량과 층화평균은 경우에 따라 효율이 다르게 나타난 반면, 결합비 추정량은 대체로 두 방법보다 효율이 우수하게 나타나 결합비 추정량이 이중추출에 유용하게 쓰일 수 있음을 보였다.

• 한국응용곤충학회지
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• 제42권1호
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• pp.29-34
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• 2003

귤응애 성충의 표본추출법을 개발하기 위하여 2개년(2001-2002년)동안 8월부터 11월까지 잎과 열매에 대해 각 조사일에 평균밀도를 조사하였다. 잎과 열매에서 귤응애 성충 밀도의 관계를 시기별로 비교하였으며, Taylor's power law (TPL)와 Iwao's patchiness regression (IPR)을 이용하여 분산지수를 비교하였다. 잎(X)과 열매(Y)에서 귤응애 성충 밀도의 관계는 ln(Y+l)=1.029 ln(X+l)($r^2$=0.80)의 직선적인 관계가 있었으며, 열매가 성숙될수록 잎보다 열매에서 귤응애 밀도가 높아지는 경향이었다. 잎과 열매의 표본조사에서 TPL이 IPR보다 평균-분산 관계를 더 잘 나타내었으며, TPL의 기울기와 절편은 두 표본단위간, 연도간에 차이가 없었다. 정착도 0.25일 때 요방제밀도 2.0, 2.5와 3.0에서의 의사결정을 위한 표본추출조사법을 개발하였으며, 조사에 필요한 최대조사나무수(고정표본크기에서 필요 나무수)는 각각 19, 16과 15주였으며, 이 때의 의사결정임 계값 $T_{critical}$은 각각 554,609와 659였다.,609와 659였다.