• 품질경영학회지
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• 제11권1호
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• pp.44-50
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• 1983

The main factors of determining the Control Line of the Control Chart can be classified as follows: 1) sample size (n), 2) the factor that determines the spread of Control Limits (B), (3) sampling frequency (h). The determination of these factors can be explained according to the extent that occurrences of assignable cause should be detected. The purpose of this paper are two: one is for composing a model of which use should be designated for economic decision on the size of these factors leading to the Control Line of the Control Chart, the other is about what influence increasing or decreasing condition, according to changeability of the size of these factors, of expect cost can have on the economy when the Control Chart is used.

• 품질경영학회지
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• 제32권4호
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• pp.252-264
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• 2004

Variable sampling Interval (VSI) control charts vary the sampling interval according to value of the control statistic while the sample size is fixed. It is known that control charts with 2-state VSI scheme, which uses only two sampling intervals, give good statistical properties. Variable sample size (VSS) control charts vary the sample size according to value of the control statistic while the sampling interval is fixed. In the VSS scheme no optimal results are known for the number of sample sizes. It is also known that the variable sampling rate (VSR) $\bar{X}$ control chart with 2-state VSS and 2-state VSI scheme leads to large improvements In performance over the fixed sampling rate (FSR) $\bar{X}$ chart, but the optimal number of states for sample size Is not known. In this paper, the VSR Χ charts with multi-state VSS and 2-state VSI scheme are designed and compared to 2-state VSS and 2-state VSI scheme. The multi-state VSS scheme is considered to, achieve an additional improvement by switching from the 2-state VSS scheme. On the other hand, the multi-state VSI scheme is not considered because the 2-state scheme is known to be optimal. The 3-state VSS scheme improves substantially the sensitivity of the $\bar{X}$ chart especially for small and moderate mean shifts.

• 품질경영학회지
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• 제14권2호
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• pp.2-8
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• 1986

This thesis is concerned with the design of control chart based on the sample median which is easy to use in practical situations and to analyze the properties for non-normally distributed Weibull process. In this cases are use to the quality characteristics of the process are not normally distributed but skewed due to the intermitted production, small lot size and sample size is small one n=3 or n=5, etc. And when it relates unsymmetrically distributed process, model designed median control chart is more effective than Shewhart $\bar{x}$-chart which assumed on normal distribution, when we exactly should be known Weibull distribution or estimated. The median control chart in this thesis is more robustness compared with other conventionally developed control chart.

• 한국경영과학회지
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• 제30권4호
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• pp.1-14
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• 2005

We propose a VSSI-CRL(Variable Sampling Size and Samplina Interval-Conforming Run length) synthetic control chart in order to improve the statistical characteristics of both the VSSI chart and the CRL synthetic chart. The VSSI-CRL chart utilizes VSSI sampling scheme, but it produces a signal only when the CRI is less than a given limit. An algorithm for calculating the ARL(Average Run length) and ATS(Average Time to Signal) of the VSSI-CRL chart is developed by employing Markov chain method. We present some lemmas for describing the statistical characteristics of the VSSI-CRL chart under in-control state. A procedure for designing the VSSI-CRL chart is proposed based on the lemmas. Extensive comparative studios show that the VSSI-CRL chart is superior to the CRL synthetic chart or the VSSI chart in general, and is comparable to the EWMA chart in ATS performance.

• 복식문화연구
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• 제3권2호
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• pp.307-321
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• 1995

The purpose of this study is to make the size chart of the child's ready-made upper garnet. For his study, we used the 1992 national anthropometric database. The results obtained are as follows. (1) It is known that the bust girth-based size chart is better than the age-based one. (2) The size range of the bust girth was 55∼73 cm to the size of the child's upper garment, and the number of the size was 7. Then the cover-rate was 86%. (3) In this study, the unisex chart was newly made because it was hardly difficult to find the actual size difference between boys and girls.

• 산업경영시스템학회지
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• 제27권2호
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• pp.114-122
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• 2004

In statistical process control applications, variable sample size (VSS) $\bar{X}$ chart is often used to detect the assignable cause quickly. However, it is usually assumed that only one assignable cause results in the out-of-control in the process. In this paper, we propose the algorithm to minimize the function of cost per unit time and compare the economic design and the statistical design by use of the value of cost per unit time. We consider double assignable causes to occur with compound in the process and adopt the Markov chain approach to investigate the statistical properties of VSS $\bar{X}$ chart. A procedure that can calculate the control chart's parameters is proposed by the economic design.

• 한국안광학회지
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• 제18권4호
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• pp.549-554
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• 2013

목적: 소수시력 단계별 시표 식별 최소조도와 대비도와 조도에 따른 개인별 시표 식별능력 차이를 알아보고자 하였다. 방법: 소수시력 단계별 10단계의 대비도로 구분되는 검사거리 3 m용 란돌트시표를 제작하였다. 69안을 대상으로 대비도 100% 시표를 사용하여 시력 단계별 식별 최소조도를 측정하였다. 시력단계별 식별 최소조도와 230 lx 상태에서 각각 식별할 수 있는 최저 시표 대비도를 측정하였다. 결과: 소수시력 단계별로 대비도 100% 시표를 식별하는 최소조도는 시표크기가 작아질수록 더 높게 측정되었다. 시력 1.0을 식별하는 평균 조도는 $74.39{\pm}25.90$ lx, 69안의 측정 범위는 17~107 lx 였다. 최소조도 상태와 230 lx 상태에서 식별가능한 최저 시표 대비도를 측정한 결과, 두 조건 모두에서 시표의 크기가 작아질수록 최저 대비도는 높아졌으며, 69안 간의 식별 최저 시표 대비도 차이도 증가되었다. 결론: 굴절교정을 위한 검사에서 조명조건이나 대비도에 따른 개인별 시표 식별능력 차이를 고려해 볼 필요가 있다.

• 품질경영학회지
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• 제31권1호
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• pp.132-141
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• 2003

As the technology has improved and demands of customers have varied, a lot of products are getting diverse and intricate. Consequently, the enterprise that produce products have to simultaneously consider the various variables for the very products. There are some scheme, such as Multivariate control chart and Demerit control chart, designed to simultaneously monitor the variables in the process. In this paper, we present an effective method for process control using the Demerit-CUSUM control chart in the process where nonconforming units or nonconformities are occured by various types. In addition, we show interpretation method for abnormal signal in order to quickly detect the assignable causes as Demerit-CUSUM control chart signals abnormality. we compare performance of Demerit control chart and Demerit-CUSUM control chart using example again used in the existing studies, and present result of performance accoriding to changing sample size and parameter.

• Communications for Statistical Applications and Methods
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• 제22권5호
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• pp.519-530
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• 2015

The geometric chart has proven more effective than Shewhart p or np charts to monitor the proportion nonconforming in high-quality processes. Implementing a geometric chart commonly requires the assumption that the in-control proportion nonconforming is known or accurately estimated. However, accurate parameter estimation is very difficult and may require a larger sample size than that available in practice in high-quality process where the proportion of nonconforming items is very small. Thus, the error in the parameter estimation increases and may lead to deterioration in the performance of the control chart if a sample size is inadequate. We suggest adjusting the control limits in order to improve the performance when a sample size is insufficient to estimate the parameter. We propose a linear function for the adjustment constant, which is a function of the sample size, the number of nonconforming items in a sample, and the false alarm rate. We also compare the performance of the geometric charts without and with adjustment using the expected value of the average run length (ARL) and the standard deviation of the ARL (SDARL).

• Journal of the Korean Data and Information Science Society
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• 제28권2호
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• pp.451-459
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• 2017

There are many researches showing that when a process change has occurred, variable sampling intervals (VSI) control chart is better than the fixed sampling interval (FSI) control chart in terms of reducing the required time to signal. When the process engineers use VSI control procedure, frequent switching between different sampling intervals can be a complicating factor. However, average number of samples to signal (ANSS), which is the amount of required samples to signal, and average time to signal (ATS) do not provide any control statistics about switching performances of VSI charts. In this study, we evaluate numerical switching performances of multivariate VSI EWMA chart including average number of switches to signal (ANSW) and average switching rate (ASWR). In addition, numerical study has been carried out to examine how to improve the performance of considered chart with accumulate-combine approach under several different smoothing constant and sample size. In conclusion, process engineers, who want to manage the correlation coefficients of related quality variables, are recommended to make sample size as large and smoothing constant as small as possible under permission of process conditions.