• Journal of Korean Institute of Industrial Engineers
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• v.16 no.1
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• pp.1-15
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• 1990

An AQL type variables sampling system with switching rules is proposed. Comparative studies of existing variables sampling standards - MIL-STD-414, ANSI Z1.9, ISO 3951, and BS 6002 - are made, and simulation studies on switching procedures are conducted. Based on comparative and simulation studies, a variables sampling standard for Korean industry is proposed. The master sampling tables of the proposed standard are taken from the variables standard ANSI Z 1. 9 and the switching rules are matched to the attributes standard KS A 3109 to enable us to move between the proposed variables standard and KS A 3109. Composite OC and ASN curves of the proposed standard are calculated for selected combinations of lot sizes and AQL's and they are compared with those of ANSI Z1.9.

• Journal of Korean Society for Quality Management
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• v.30 no.1
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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.

• Structural Engineering and Mechanics
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• v.32 no.1
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• pp.1-20
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• 2009

The present contribution addresses uncertainty quantification and uncertainty propagation in structural mechanics using stochastic analysis. Presently available procedures to describe uncertainties in load and resistance within a suitable mathematical framework are shortly addressed. Monte Carlo methods are proposed for studying the variability in the structural properties and for their propagation to the response. The general applicability and versatility of Monte Carlo Simulation is demonstrated in the context with computational models that have been developed for deterministic structural analysis. After discussing Direct Monte Carlo Simulation for the assessment of the response variability, some recently developed advanced Monte Carlo methods applied for reliability assessment are described, such as Importance Sampling for linear uncertain structures subjected to Gaussian loading, Line Sampling in linear dynamics and Subset simulation. The numerical example demonstrates the applicability of Line Sampling to general linear uncertain FE systems under Gaussian distributed excitation.

• Journal of Korean Society for Quality Management
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• v.25 no.3
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• pp.22-38
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• 1997

In a traditional sequential acceptance sampling plan, it is assumed that the sampled items are independent each other. In this paper, stochastically dependent sequential acceptance sampling plans are dealt when there exists dependency between sampled items. Monte-Calro algorithm is used to find the acceptance and rejection probabilities of a lot. The number of defectives for the test to be accepted and rejected in probability ratio sequential test can be found by using these probabilities. The formula for measures of performance of these sampling plans is developed. Type I and II error probabilities are estimated by simulation. This research can be a, pp.ied to sequential sampling procedures in place of control charts where there is a recognized and necessary dependency during the production processes. Also, dependent multiple acceptance sampling plans can be derived by extending this sequential sampling procedure. As a numerical example, a Markov dependent process model is given, and the characteristics of the sampling plans are examined according to the change of the dependency factor.

• Journal of Soil and Groundwater Environment
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• v.18 no.1
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• pp.94-101
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• 2013

It is well known that uncertainty associated with soil sampling is bigger than that with analysis. In this research, uncertainties for soil sampling when assessing TPH and BTEX concentration in soils were quantified based on actual field data. It is almost impossible to assess exact contamination of the site regardless how carefully devised for sampling. Uncertainties associated with sample reduction for further chemical analysis were quantified approximately 10 times larger than those associated with core sampling on site. Bigger uncertainties occur when contamination level is low, sample quantity is small, and soil particle is coarse. To minimize the uncertainties on field, homogenization of soil sample is necessary and its procedures are proposed in this research as well.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.6 no.9
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• pp.1-5
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• 1983

This study takes over the application of survey sampling theory to activity sampling and the application of activity sampling to time standard estimation. Cluster, stratified, and multistage sampling are studied in conjunction with random and systematic sampling. Estimation procedures that will maximize the information obtained per cost expended on the study and specification of the procedure to be used to estimate the accuracy of the estimates for the adopted procedure are considered. The use of multiple regression md linear programming to estimate standard element performance time from typical job lot production data is also considered.

• Journal of Korean Society for Quality Management
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• v.21 no.1
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• pp.35-43
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• 1993

The principal objective of a sampling plan is to make efficient use of the budget allocated and to obtain as precise an estimate of a population parameter as possible. In order to estimate the proportion of defectives produced or to determine some measure of product Quality, it is necessary to select random samples which represent a population parameter of the process. In this case, the two stage sampling is more efficient and convenient than simple random sampling. Therefore this paper aims to propose the design procedures of two stage sampling plan to obtain a representative samples in considering the sampling precision under the restricted sampling unspection cost.

• The Korean Journal of Applied Statistics
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• v.7 no.1
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• pp.1-17
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• 1994

This article basically considers the calibration problem with censored data from the Bayesian point of view. The Gibbs sampling method is discussed to solve the difficulty encountered in computing the posterior distribution. Also presented is an approach for impementing the Gibbs sampling in actual data situation with the estimation procedures.

• Survey Research
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• v.11 no.2
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• pp.141-160
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• 2010

This study aims to analyze the usefulness of the survey procedures developed for telephone surveys using a random sampling method. We conducted a telephone survey of residents in a local area from October 26 to November18,2009. We applied random sampling procedures with five call-backs. Particular attention was given to the conversion of refusals. Out of 2,454 phone numbers, we succeeded in getting responses from 637 numbers. The absence of residents was the primary cause of non-response. We received responses from 45.7% of those with whom we successfully made contact. One finding of this study is that, contrary to our initial expectations, call-backs do not significantly increase the percentage of responses from young people. Also we cannot find any significant differences in responses to various questions between the responses received from the first round of calls and later responses. However, these results are not conclusive; another survey may produce different results. Therefore, further research is needed.

• Safety and Health at Work
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• v.4 no.2
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• pp.111-116
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• 2013

Background: The aim of this study was to evaluate the quality of the Second Korean Working Conditions Survey (KWCS), focusing on its validity and reliability. Methods: The external validity was evaluated by the assessment of sampling procedures and the response rate, in order to investigate the representativeness of the sample. The content validity was evaluated by the assessment of the development of the questionnaire, and the consistency of questions for the selected construct. The test-retest method was used to evaluate the reliability by means of a phone call survey of 30% of the respondents, who were randomly selected. The respondents' satisfaction regarding the survey procedures and interview time were analyzed to evaluate the quality of survey data. Results: The external validity was assured by an acceptable sampling procedure, rigid multi-stage stratified cluster random sampling. The content validity was also guaranteed by a reasonable procedure for the development of the questionnaire with a pretest. The internal consistency of the questions for work autonomy was maintained, with 0.738 of Cronbach's alpha. The response rate of 36% was lower than that of the European Working Conditions Survey (EWCS), with a contact rate of 66%, compared to 76% for the EWCS. The matching rates of the five retested questions were more than 98% reliable. Conclusion: The quality of the second KWCS was assured by the high external and content validity and reliability. The rigid sampling procedure and development of the questionnaire contributed to quality assurance. The high level of reliability may be guaranteed by the sophisticated field survey procedures and the development of a technical manual for interviewers. The technical strategies for a high response rate should be developed for future surveys.