| The control variable and the algorithms used to calculate the warning and action limits are determined for each track. |
| A control variable is any factor that remains unchanged and strongly influences values. |
| Apart from the control variable, each track on the control chart also contains control limits for the process. |
| The times Tu and Tg are derived from the progress of the actual value of the control variable. |
| These measures were used to create the study's control variable in the multivariate analyses. |
| Note that in thermally slow systems the actual value of the control variable may continue to rise after the controller has been switched off. |
