| The key results in the study are robust to the choice of fathers' over mothers' average education as the control variable. |
| Apart from the control variable, each track on the control chart also contains control limits for the process. |
| The motor is switched off as soon as the stroke position, which is equivalent to the received control variable, has been reached. |
| If incorrectly applied, this can result in impermissible values of the control variable. |
| Job tenure is measured as the number of weeks worked at the job and is included as a control variable. |
| The times Tu and Tg are derived from the progress of the actual value of the control variable. |
