Hotelling T2 Chart

The Hotelling T2 chart is a multivariate generalization of the standard X-bar (and R, S) chart for variables (characteristics; see also Shewhart Control Charts). Instead of controlling single X values or means, and standard deviations, the Hotelling T2 chart allows for the control of a vector of means for multiple characteristics, and the variance/covariance matrix of the variables to control process variability (in a Generalized Variance Chart). These simple (from a user's perspective) charts can be used to monitor effectively tens of variables (characteristics) simultaneously in a single chart. When an out-of-control condition occurs, typically a follow-up Pareto (-like) chart can be created to indicate which variables are most likely responsible for the alarm; these variables can then be further examined in standard X or X-bar and S charts.

See also STATISTICA Multivariate Quality Control for details.

The Hotelling T2 chart is also used in STATISTICA Multivariate SPC for multivariate control charts of factor (PCA/PLS) scores.