Standardized Q-statistic for improved sensitivity in the monitoring of residuals in MSPC

This paper presents the standardized e-statistic for monitoring residuals o f latent variable models in multivariate statistical process control (MSPC) . Before the summation of the squared residuals, they are scaled according to their expected variation obtained from normal operating conditions (NOC) data. Data from a simulated batch process and from an industrial batch pro cess are used to show that this scaling improves the sensitivity of the Q-s tatistic considerably. The standardized e-statistic is introduced for the o ff-line monitoring of batch processes, but it can also be used for the moni toring of continuous processes as well as for the on-line monitoring of bat ch processes. Copyright (C) 2000 John Wiley & Sons, Ltd.