• Communications for Statistical Applications and Methods
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• v.6 no.1
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• pp.143-150
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• 1999

Ko(1998) proposed a procedure to enhance the efficiency of double sampling plans by allowing second-stage sample size and critical region to depend on first-stage evidence using constraint optimization approaches. In this study further developments of such plans by incorporating several practically possible researcher's aims into the optimization are considered. Comparisons are made with the optimal ordinary double sampling plan and also among them It is observed that it is to some extent possible to match the details of the optimization to certain qualitative methodological aims.

• The Korean Journal of Applied Statistics
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• v.11 no.2
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• pp.403-413
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• 1998

Sample size determination is a crucial part of sampling design. This paper gives a assessment for sample size determination using two-stage sampling scheme for estimating the population mean with a given precision.

• Journal of the Korean Statistical Society
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• v.30 no.4
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• pp.637-644
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• 2001

We investigated two kinds of mean square error (MSE) estimator of homogeneous linear estimator (HLE) for the population total under stratified multi-stage sampling. One is studied when the second stage variance component is estimable and the other is found in cafe it is not estimable. The proposed estimators are necessary forms of non-negative unbiased MSE estimators of HLE.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.17 no.1
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• pp.79-86
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• 1999

In this study, we investigated methods of quality check for digital basemaps and proposed effective methods of quality check. We used new statistical methods for quality control in order to carry out quality check for digital basemaps. We proposed 2-stage complete sampling and 2-stage cluster sampling method to improve present statistical methods of quality check(1-stage complete sampling method). We estimated error rate and number of omitted objects using simulated data about all delivered digital basemaps and estimated variances about it. We could determine confidence interval about error rate and number of omitted objects.

• The Korean Journal of Applied Statistics
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• v.8 no.2
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• pp.99-108
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• 1995

When modeling a complicated system with a computer model, it is of vital importance to choos input values efficiently. The Latin Hypercube sampling (LHS) proposed by MaKay et al.(1979) has been most widely used for choosing input values for a computer model. We propose the two-stage Latin Hypercube sampling(TLHS) which is an improved version of the LHS for procucing input values in estimating the excectation of a function of the output variable. The proposed method is applied to simulation study of the performance of a printer actuator and it is shown to outperform the other sampling methods including the LHS in accuracy.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.23 no.4
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• pp.348-355
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• 2013

Objectives: In working environment measurement, sampling is an important stage for obtaining reliable result as analysis. A personal air sampling pump is one of the most fundamental and important element in the work environment measurement, but it remains at the level of calibrating the flow rate of the pump before and after sampling. There is no checking whether the flow rate set at the initial stage would be hold during sampling. The purpose of this study was to develop a method to evaluate the flow rate performance of particulate sampling pump with three-pieces cassette holder containing filters commonly used to sample particulate. Materials and methods: We tested back pressure of particulate sampling pumps commonly used in Korea with three-pieces cassette holder containing various filters, and tried to find out the combination conditions of filters in accordance with back pressure required by ISO standard 13137. Results: We found out the matrix of sampling media such as three-pieces cassette holder containing filters applicable to the pressure drop required by the ISO standard for evaluating the flow rate stability under increasing pressure drop and long term(8 hour) performance. Conclusions: This evaluation method using sampling media matrix for checking flow rate stability proposed by this study could be very useful tool to find out good performance pumps before sampling.

• Journal of Preventive Medicine and Public Health
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• v.42 no.2
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• pp.135-142
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• 2009

Objectives : An appropriate sampling strategy for estimating an epidemiologic volume of diabetes has been evaluated through a simulation. Methods : We analyzed about 250 million medical insurance claims data submitted to the Health Insurance Review & Assessment Service with diabetes as principal or subsequent diagnoses, more than or equal to once per year, in 2003. The database was re-constructed to a 'patient-hospital profile' that had 3,676,164 cases, and then to a 'patient profile' that consisted of 2,412,082 observations. The patient profile data was then used to test the validity of a proposed sampling frame and methods of sampling to develop diabetic-related epidemiologic indices. Results : Simulation study showed that a use of a stratified two-stage cluster sampling design with a total sample size of 4,000 will provide an estimate of 57.04%(95% prediction range, 49.83 - 64.24%) for a treatment prescription rate of diabetes. The proposed sampling design consists, at first, stratifying the area of the nation into "metropolitan/city/county" and the types of hospital into "tertiary/secondary/primary/clinic" with a proportion of 5:10:10:75. Hospitals were then randomly selected within the strata as a primary sampling unit, followed by a random selection of patients within the hospitals as a secondly sampling unit. The difference between the estimate and the parameter value was projected to be less than 0.3%. Conclusions : The sampling scheme proposed will be applied to a subsequent nationwide field survey not only for estimating the epidemiologic volume of diabetes but also for assessing the present status of nationwide diabetes control.

• Journal of the Korean Statistical Society
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• v.12 no.1
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• pp.36-45
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• 1983

After every decennial census in the U.S., national surveys such as the Consumer Expenditures surveys are redesigned. The redesigned samples will be multi-stage systematic samples. Many sampling schemes have been proposed for comparison which requires the estimation and variance estiamtion formula. This paper deals with the surveys redesign research which concerns the sample design within the Primary Sampling Unit (PSU). In constructing the estimators it deals with the problem of which first stage inflation factor to use. The expected value of the proposed estimators is also derived.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.6
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• pp.116-123
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• 1998

An interferometric microscope with an improved lateral resolution is presented. The nanometer resolution XY stage is integrated into standard temporal phase shifting interferometer. The nanometer resolution XY stage is used to position specimen in subpixel of CCD detector, therefore CCD detector's sampling is improved. Two scanning algorithms and those simulation results are also presented. The simulation results show that scanning algorithms improve CCD detector's sampling significantly, and interferometeric microscope's lateral resolution is improved also.

• Communications for Statistical Applications and Methods
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• v.6 no.3
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• pp.749-754
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• 1999

The cost is known to be proportional to the size of sample. We consider a cost function of the form Cost=c1np+c2npmq where c1, c2 p, and q are all positive constants. This cost function is to be used in finding an optimal allocation in two-stage cluster sampling. The optimal allocations of n and m gives the properties of uniqueness under some conditions and of monotonicity with p>0 when q=1.