What characterizes special causes on a control chart?

Special causes on a control chart are characterized by unexpected variations outside standard deviations. This type of variation indicates that there is an external factor or a unique occurrence affecting the process being monitored. Unlike common causes, which produce inherent variations within the process and can be expected over time, special causes signify that something atypical has happened that requires investigation and possibly corrective action.

When a control chart displays data points that fall outside the established control limits, it signals that the process is not operating as usual and that these irregularities are potentially significant. Addressing special causes is critical in quality improvement because they can lead to defects or inefficiencies if not resolved.

In contrast, constant fluctuations, predictable outcomes, and tight clustering relate more closely to common cause variation, where the process is in a stable state and variations occur consistently within the expected range. Recognizing the distinction between common and special causes is essential for effective quality management and process improvement.