Generalized contribution plots in multivariate statistical process monitoring

This paper discusses contribution plots for both the D-statistic and the Q- statistic in multivariate statistical process control of batch processes. C ontributions of process variables to the D-statistic are generalized to any type of latent variable model with or without orthogonality constraints. T he calculation of contributions to the Q-statistic is discussed. Control li mits for both types of contributions are introduced to show the relative im portance of a contribution compared to the contributions of the correspondi ng process variables in the batches obtained under normal operating conditi ons. The contributions are introduced for off-line monitoring of batch proc esses, but can easily be extended to on-line monitoring and to continuous p rocesses, as is shown in this paper. (C) 2000 Elsevier Science B.V. All rig hts reserved.