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Improving the Sensitivity of the T2 Statistic in Multivariate Process Control

Summary: [This abstract is based on the authors' abstract.] The T2 statistic in multivariate process control is a function of the residuals taken from a set of linear regressions of the process variables. These residuals are contained in the conditional T2 terms of the orthogonal decomposition of the statistic. It is shown that a large residual in one of these fitted models can be due to incorrect model specification. By improving model specification at the time that the historical data set is constructed, it may be possible to increase the sensitivity of the T2 statistic to signal detection. The resulting regression residuals also can be used to improve the sensitivity of the T2 statistic to small but consistent process shifts. This is accomplished using plots that are similar to cause-selecting control charts.

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  • Topics: Statistical Process Control (SPC)
  • Keywords: Control charts,Hotelling's T2 statistic,Process control,Decomposition,Multivariate control charts
  • Author: Mason, Robert L.; Young, John C.
  • Journal: Journal of Quality Technology