• 산업경영시스템학회지
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• 제10권16호
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• pp.183-195
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• 1987

The effectiveness of quality control is contingent to adaptability to the present circumstance. The objectives of this study are to provide empirical data to carry out qualify control effectively. To accomplish this purpose, an empirical study was made by questionaire (mailing survey method, Feb. to Mar. in 1987). The sample is the 167 companies in Korean manufacturing industry. The main findings out of the analysis are as follows the stage of quality control is concentrated in appraisal phase, the company standard is equiped gradually in non-KS marked company and the need of economic evaluation about quality control is increased gradually. With a view to analysing of relationship between quality control and it's effect factors (company standard, KS mark, computer based information system), the methods of $\chi$$^2$ test are used. The company standard have a significant difference in top manager's altitude to duality control, operation stage of quality control. operation scope of qualify control and quality budgeting system but is insignificant with economic evaluation about duality control. Otherwise, KS mark is insignificant with the equality control activity except for operation scope. The quality information system based in computer have a significant difference in operation stage, operation scope and economic evaluation. Therefor, for the purpose of attaining effectiveness of quality control through the economic evaluation about quality control, the company standard and computer based duality information system must be utilized in quality control activity.

• Communications for Statistical Applications and Methods
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• 제27권1호
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• pp.65-77
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• 2020

Geometric charts are effective in monitoring the fraction nonconforming in high-quality processes. The in-control fraction nonconforming is unknown in most actual processes; therefore, it should be estimated using the Phase I sample. However, if the Phase I sample size is small the practitioner may not achieve the desired in-control performance because estimation errors can occur when the parameters are estimated. Therefore, in this paper, we adjust the control limits of geometric charts with the bootstrap algorithm to improve the in-control performance of charts with smaller sample sizes. The simulation results show that the adjustment with the bootstrap algorithm improves the in-control performance of geometric charts by controlling the probability that the in-control average run length has a value greater than the desired one. The out-of-control performance of geometric charts with adjusted limits is also discussed.

• 품질경영학회지
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• 제32권4호
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• pp.169-183
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• 2004

The synthetic control chart (SCC) proposed by Wu and Spedding (2000) is to detect shifts in the process mean. The performance was re-evaluated by Davis and Woodall (2002), and the steady-state average run length (ARL) performance was shown to be inferior to cumulative sum (CUSUM) or exponentially weighted moving average (EWMA) chart This paper proposes a simple adaptive scheme to improve the performance of the synthetic control chart. That is, once a non-conforming (NC) sample occurs, we investigate the next L-consecutive samples with larger sample sizes and shorter sampling intervals. We employ a Markov chain model to derive the ARL and the average time to s19na1 (ATS). We also propose a statistical design procedure for determining decision variables. Comprehensive comparative study shows that the proposed control chart is uniformly superior to the original SCC or double sampling (DS) Χ chart and comparable to the EWMA chart in ATS performance.

• 품질경영학회지
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• 제18권1호
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• pp.77-83
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• 1990

A model for the economic design of an pn control charts with an assignale cause is presented and the loss-cost function for control schemes using these charts is derived. By minimizing this function with respect to the three control variables, namely, the sample size, the sampling interval and acceptance number, the economically optimal control plan can be optained. The article shows what influence increasing or decreasing condition, according to changeability of the size of these factors, of expected cost can have on the economy when an attribute control chart is used.

• 응용통계연구
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• 제4권1호
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• pp.65-83
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• 1991

우리나라 기업의 통계적 품질관리 기법의 활용 현황을 알아보기 위하여 전국 4,500여개의 제조업체에 대하여 설문조사를 하여 설문에 응한 2,586개 제조업체의 설문결과에 대하여 통계적 분석을 행하고, 통계적 기법활용의 문제점과 그 대책을 제시했다.

• 한국식품과학회지
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• 제34권4호
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• pp.642-646
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• 2002

본 연구에서는 기능성 쌀을 이용한 쿠키를 개발하여 이화학적 관능적 품질 특성을 조사하였다. 반죽의 pH는 기능성 쌀가루를 10% 대체한 반죽이 대조군 보다 유의적으로 높은 pH를 나타내었다. 쿠키의 퍼짐성에서는 20%와 30% 대체한 시료군이 대조군 보다 유의적으로 높은 퍼짐성을 보였다. 시료군의 L값은 대조군이 69.31으로 가장 높았으며, b값은 20%대조 시료군이 35.60의 값으로 가장 높았다. 기능성 쌀가루를 다양한 수준으로 대체한 쿠키의 관능검사를 실시한 결과 기능성 쌀가루를 10% 대체한 시료군이 고소한 냄새, 고소한 맛, 경도, 색의 갈색정도에서 유의적으로 특성이 강하게 평가되었다. 쿠키의 기호도 검사 결과 쿠키의 전반적인 기호도에서 기능성 쌀가루를 20%와 30% 대체한 시료가 대조군과 함께 유의적으로 높은 기호도를 나타내었다. 따라서 기능성 쌀가루로 대체된 쿠키는 모든 대체비에서 대조구와 비교하였을 때 유의적인 차이가 없거나 유의적으로 높은 기호도를 나타내어 기능성 쌀쿠키 개발의 가능성을 보여주었다.

• Preventive Nutrition and Food Science
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• 제20권4호
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• pp.292-297
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• 2015

The objective of this study was to compare the effects of adding lactic acid and pectinase, and chaptalization for the quality of apple wine and the production of hazardous compounds (methanol and acetaldehyde). The pH of all of the samples was below 4; therefore, mash seemed to be fermented without any issue. Total acidity was the highest in sample A due to lactic acid addition. Pre-treated groups (samples B, C, and D) showed higher total acidities than that of the control (P<0.05). Pre-treatments might influence the production of organic acids in apple wines. The control and pectinase added sample (sample B) had the lowest alcohol contents. Adding lactic acid produced more alcohol, and chaptalized samples produced more alcohol due to the addition of sugar. Adding pectinase with and without chaptalization was not effective for producing more alcohol. The control sample had significantly higher acetaldehyde content (2.39 mg/L) than the other samples (1.00~2.07 mg/L); therefore, pre-treatments for apple wine fermentation produced a lower amount of acetaldehyde. Among the pre-treated samples, samples C and D showed the lowest acetaldehyde content of 1.00 mg/L and 1.16 mg/L, respectively. On the other hand, a significantly higher amount of methanol was generated for sample A (1.03 mg/L) and sample D (1.22 mg/L) than that of the control (0.82 mg/L) (P<0.05). Adding lactic acid or chaptalization was effective in reducing methanol and acetaldehyde in apple wines.

• 품질경영학회지
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• 제23권4호
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• pp.1-12
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• 1995

Sample skewness has not received much attention from researchers to design a control chart. In this paper, control charts based on two skewness measures are studied to control a manufacturing process. One skewness measure is the third central moment about mean, the other is the third L-moment which is a linear combination of order statistics. Since the exact sampling distributions of two skewness measures are unknown, empirical sampling distributions are studied using simulation. The sampling distributions are used to design control charts for skewness and performance of two skewness measures is compared.

• 품질경영학회지
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• 제30권2호
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• pp.99-117
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• 2002

Variable sampling interval(VSI) and variable sample size(VSS) control charts vary the sampling rate for the next sample depending on the current chart statistic. This paper develops EWMA charts with the VSI and VSS features, and investigates the effectiveness of these charts in context of an economic model. The economic properties of these charts are evaluated by using Markov chain methods. The model contains cost parameters which allow the specification of the costs associated with sampling, false alarms, and operating off target. This economic model can be used to quantify the cost saving that can be obtained by using control charts with the VSI and VSS features instead of with the fixed sampling rate(FSR) feature, and can also be used to gain insight into the way that control charts with the VSI and VSS features should be designed to achieve optimal economic performance. The economic performance of X charts with the VSI and VSS features is also considered.

• 품질경영학회지
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• 제36권1호
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• pp.7-19
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• 2008

During the past two decades, a huge amount of research on adaptive control charts has been accomplished. Especially, variable sampling interval (VSI), variable sample size (VSS), and variable sample size and sampling interval (VSSI) charts have been focused by many researchers due to their simplicity and efficiency. On the other hand, the difference among notations, assumptions, methodologies may cause confusions in per forming further studies or practical implementations. This research analyses and compares diverse models so as to provide a unified view on statistical and economical characteristics. As a result, we perform comparative study on economical design models of VSI, VSS, and VSSI charts, respectively, We also present practical guidelines to utilize those adaptive control charts.