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Multivariate Control Charts for Individual Observations

 

作者: TracyNola D.,   YoungJohn C.,   MasonRobert L.,  

 

期刊: Journal of Quality Technology  (Taylor Available online 1992)
卷期: Volume 24, issue 2  

页码: 88-95

 

ISSN:0022-4065

 

年代: 1992

 

DOI:10.1080/00224065.1992.12015232

 

出版商: Taylor&Francis

 

关键词: Multivariate Quality Control;T2Control Charts

 

数据来源: Taylor

 

摘要:

Whenpcorrelated process characteristics are being measured simultaneously, often individual observations are initially collected. The process data are monitored and special causes of variation are identified in order to establish control and to obtain a“clean”reference sample to use as a basis in determining the control limits for future observations. One common method of constructing multivariate control charts is based on Hotelling'sT2statistic. Currently, when a process is in the start-up stage and only individual observations are available, approximateFand chi-square distributions are used to construct the necessary multivariate control limits. These approximations are conservative in this situation. This article presents an exact method, based on the beta distribution, for constructing multivariate control limits at the start-up stage. An example from the chemical industry illustrates that this procedure is an improvement over the approximate techniques, especially when the number of subgroups is small.

 

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