An Application of Variable Sampling Interval Control Charts
作者:
BaxleyRobert V.,
期刊:
Journal of Quality Technology
(Taylor Available online 1995)
卷期:
Volume 27,
issue 4
页码: 275-282
ISSN:0022-4065
年代: 1995
DOI:10.1080/00224065.1995.11979607
出版商: Taylor&Francis
关键词: Average Run Length;Exponentially Weighted Moving Average Control Charts;Quality Costs;Statistical Process Control;Variable Sampling Intervals
数据来源: Taylor
摘要:
Variable Sampling Interval (VSI) control charts have been studied extensively, and it has been shown for Shewhart, cumulative sum (CUSUM), and exponentially weighted moving average (EWMA) charts that shifts in the process mean can be detected more quickly with no increase in the average in-control sampling or false alarm frequency relative to fixed interval charts. Applications of VSI charts in industry have been few, however, primarily due to logistical problems associated with a variable sample schedule. In this paper, we present an application of a VSI-EWMA chart at Monsanto's nylon fiber plant in Pensacola, Florida. Motivation for this implementation, instead of being quicker detection of shifts, was a significant decrease in laboratory cost with little adverse impact on control chart performance compared with the fixed-interval EWMA chart. The logistical problems were solved by employing a fixed time option with the VSI scheme (VSI-FT), where there is a fixed sample schedule for the long interval, and in-between samples are taken when warranted by the data.
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