• Journal of Korean Society for Atmospheric Environment
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• v.14 no.5
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• pp.507-518
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• 1998

A field comparison study was carried out to quantify differences among various sampling and analytical methods for volatile organic compounds (VOCs) at a site in Vlsan in June 1997. Air sampling containers (SUMMA canisters) were used by the Korea Institute of Science and Technology (KIST) and adsorption tubes (carbotrap) were used by Yeungnam University (YN Univ.) for sampling ambient air. Duplicate samples obtained by KIST were analyzed by KIST with a GC-MS system for aromatics and halogenated hydrocarbons and by Atm AA with a GC -FID system for C2∼C9 hydrocarbons, respectively. The adsorption tube samples were analyzed by YN Univ. with a GC-FID system for aromatics. VOC levels for the duplicate canister sampls analyzed by KIST and Atm AA were in good agreement. Concentrations of aromatics by the adsroption tube method were generally higher than those by the canister sampling method by factor of 1.5 to 2.0. Differences between the two sampling methods were discussed.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.32B no.1
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• pp.110-119
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• 1995

The lateral resolution in an ultrasound imaging system is one of the most important factors for quality of the image and is determined by the beam focusing. For the better lateral resolution SDF(Sampled Delay Focusing) capable of digital focusing was proposed. The second-order sampling, one of band-width sampling methods, is suggested as being the best suitable for SDF because it allows total digital processing and is simple and economical. By proving that it introduces too much error, this article shows the second-order sampling is not appropriate for sampling of the wide-band signal generally used in ultrasound imaging systems. Also, this article suggests new sampling methods that maintain the advantages and reduce the unavoidable errors of the second-order sampling method. From computer simulation it is expected that the proposed methods reduce the errors of the second-order sampling method and can be used in real applications.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.8 no.11
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• pp.85-95
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• 1985

This thesis is a study on the work sampling method which is one of the important parts in the fields of work measurement today. The primary objective of this study is to examine various methods of selecting observation times in work sampling studies, including simple random systematic, and stratified sampling and a new method called restricted random sampling. The attribute of these sampling methods are explained, particulary statistical efficiency, and the important advantages of stratification are analysed. A case study of work sampling was made in a manufacturing plant to show its practical application and the effectiveness of the stratified random sampling technique.

• Quality Improvement in Health Care
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• v.29 no.2
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• pp.85-93
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• 2023

Purpose: The predominant approach for mitigating inadequate sampling rates has primarily involved bolstering the volume of education. This study aimed to curtail inadequate sampling rates through the implementation of continuous quality improvement (CQI) activities, tailoring effective methods to the unique needs of each institution. Methods: We developed a sample handling guidebook and implemented QI activities to address this issue. Results: These measures resulted in a 4.7% decrease in inadequate sampling rates, concurrently improving knowledge of sample handling and overall nurse satisfaction. We addressed the root causes of inadequate sampling before laboratory pre-processing by: 1) focusing on systematic rather than erratic errors through CQI activities, 2) revising the sample handling guide, and 3) delivering face-to-face education based on the specific needs of the nursing department. These changes resulted in an additional 0.6% decrease in the inadequate sampling rate. Conclusion: This study demonstrates that the implementation of CQI activities based on evidence derived from a multifaceted causal analysis significantly reduced the inadequate sampling rate compared to previous studies.

• Communications for Statistical Applications and Methods
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• v.3 no.3
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• pp.161-168
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• 1996

This paper describes a sampling method, which can be used instead of the simple random sampling without replacement(SRSWOR). This method, circular sampling, assumes that the sampling units of the population are arranged in circular format, and randomly selects as many as samples of contiguous units. Therefore this method gathers information quicker and easier than STSWOR. In certain circumstances, the reliability of this method is better than that of STSWOR. And of circular sampling would be applied to nonprobability could be determined. methods, the reliability of the sample results in terms of probability could be determined.

• Journal of the Korea Society for Simulation
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• v.9 no.2
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• pp.75-87
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• 2000

In this paper, nonstationary multiple sampling plans are discussed which are difficult to solve by analytical method when there exists dependency between the sample data. The initial solution is found by the sequential sampling plan using the sequential probability ration test. The number of acceptance and rejection in each step of the multiple sampling plan are found by grouping the sequential sampling plan's solution initially. The optimal multiple sampling plans are found by simulation. Four search methods are developed U and the optimum sampling plans satisfying the Type I and Type ll error probabilities. The performance of the sampling plans is measured and their algorithms are also shown. To consider the nonstationary property of the dependent sampling plan, simulation method is used for finding the lot rejection and acceptance probability function. As a numerical example Markov chain model is inspected. Effects of the dependency factor and search methods are compared to analyze the sampling results by changing their parameters.

• Communications for Statistical Applications and Methods
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• v.22 no.5
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• pp.435-443
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• 2015

Two phase sampling design is useful to increase estimation efficiency using deep stratification, improved non-response adjustment and reduced coverage bias. The same sampling units are commonly used for the first and the second phases in complex two-phase sampling design. In this paper we consider a sampling scheme where the first phase sampling units are clusters and the second phase sampling units are list samples. Using selected clusters in first phase requires that we list up elements in the selected clusters from the first phase and then use the list as a secondary sampling frame for the second phase sampling design. Then we select second phase samples from the listed sampling frame. We suggest an estimator based on the complex two-phase sampling design with different sampling units of each phase. Also the estimated variances of the estimator obtained by using classic and replication variance methods are considered and compared using simulation studies. For real data analysis, 2010 Korea Farm Household Economy Survey (KFHES) and 2011 Korea Agriculture Survey (KAS) are used.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.23 no.4
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• pp.341-347
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• 2013

Objectives: The aim of this study is to investigate the differences in airborne TDI concentrations based on the filter collection method and liquid collection method and to compare airborne TDIs concentrations by sampling method change when using the filter collection method in the spray-painting process. Methods: For the sample measurement, the filter collection method(OSHA#42) and liquid collection method(NIOSH#5522) were used; for the sampling method, the full-period single sampling and full-period consecutive sampling methods were used. The samples were collected in spray-painting and drying process locations. Results: In all samples collected from the spray-painting and drying process locations through the filter collection and liquid collection methods, greater amounts of 2,6-TDI than 2,4-TDI were detected. When the TDI collection concentrations based on the sampling methods were compared, the concentrations of 2,4-TDI and 2,6-TDI collected by the consecutive sampling method were higher than the concentrations of 2,4-TDI and 2,6-TDI collected by the single sampling method for both the filter collection method and liquid collection method used in the spray-painting process. These differences were statistically significant. Conclusions: When TDI collection concentrations based on the sample measurement methods were compared, the concentration of 2,4-TDI and 2,6-TDI collected through the liquid collection method were higher than the concentrations of 2,4-TDI and 2,6-TDI collected by the filter collection method, and the differences were statistically significant. In the drying process, no difference was shown in the collection concentrations of 2,4-TDI and 2,6-TDI with the two measurement methods.

• Asian Pacific Journal of Cancer Prevention
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• v.17 no.7
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• pp.3489-3494
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• 2016

Background: A major problem with cervical cancer screening in countries which have no organized national screening program for cervical cancer is sub-optimal participation. Implementation of self-sampling method may increase the coverage. Objective: We determined the agreement of cytological diagnoses made on samples collected by women themselves (self-sampling) versus samples collected by physicians (Physician sampling). Materials and Methods: We invited women volunteers to undergo two procedures; cervical self-sampling using the Evalyn brush and physician sampling using a Cervex brush. The women were shown a video presentation on how to take their own cervical samples before the procedure. The samples taken by physicians were taken as per routine testing (Gold Standard). All samples were subjected to Thin Prep monolayer smears. The diagnoses made were according to the Bethesda classification. The results from these two sampling methods were analysed and compared. Results: A total of 367 women were recruited into the study, ranging from 22 to 65 years age. There was a significant good agreement of the cytological diagnoses made on the samples from the two sampling methods with the Kappa value of 0.568 (p=0.040). Using the cytological smears taken by physicians as the gold standard, the sensitivity of self-sampling was 71.9% (95% CI:70.9-72.8), the specificity was 86.6% (95% CI:85.7-87.5), the positive predictive value was 74.2% (95% CI:73.3-75.1) and the negative predictive value was 85.1% (95% CI: 84.2-86.0). Self-sampling smears (22.9%) allowed detection of micro-organisms better than physicians samples (18.5%). Conclusions: This study shows that samples taken by women themselves (self-sampling) and physicians have good diagnostic agreement. Self-sampling could be the method of choice in countries in which the coverage of women attending clinics for screening for cervical cancer is poor.

• Journal of Communications and Networks
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• v.18 no.5
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• pp.818-825
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• 2016

Network management and anomaly detection are challenges in high-speed networks due to the high volume of packets that has to be analysed. Flow-based analysis is a scalable method which reduces the high volume of network traffic by dividing it into flows. As sampling methods are extensively used in flow generators such as NetFlow, the impact of sampling on the performance of flow-based analysis needs to be investigated. Monitoring using sampled traffic is a well-studied research area, however, the impact of sampling on flow-based anomaly detection is a poorly researched area. This paper investigates flow sampling methods and shows that these methods have negative impact on flow-based anomaly detection. Therefore, we propose an efficient probabilistic flow sampling method that can preserve flow traffic distribution. The proposed sampling method takes into account two flow features: Destination IP address and octet. The destination IP addresses are sampled based on the number of received bytes. Our method provides efficient sampled traffic which has the required traffic features for both flow-based anomaly detection and monitoring. The proposed sampling method is evaluated using a number of generated flow-based datasets. The results show improvement in preserved malicious flows.