Reaction to Chart Signals

Section 3 Control Charts

Lesson S03-09

Text: Section 3 pages 53 – 54

Duration: 6 minutes

Reaction to Chart Signals

All chart signals should be investigated for identification of the root cause of the apparent process change (e.g. trend, shift, variation change). It is not a good strategy to “wait and see” as the opportunity to detect and uncover a detrimental root cause may be lost.

Tips to Improve Your Reaction Effectiveness

Monitoring your process closely to look for correlated events to signals is just one idea discussed here.

Updating Control Limits

A common question is, “When Should Control Limits be Updated?” Some software will allow for dynamically updated control limits in which the control limits are regularly updated based on the most recent data. This is a dangerous practice as process shifts and trends can be masked by control limits that adjust along with the trend. The only justifiable reason to update control limits is to reestablish a valid control chart following a process change (the change may be by design or an unexpected change that becomes the new norm).