Quality Assurance

444 Appendix I

• Control plans are revised and updated when products or pro-

cesses differ from those in current production.

• Process variability monitoring/reduction

• Supplier has determined appropriate statistical techniques. A

key aspect of defect prevention is process variability reduction

and the use of SPC or an equivalent process monitoring method

to indicate when action is necessary and, conversely, when pro-

cesses should be left alone.

• Operator-based SPC control charts are optimized for statistically

valid sample frequency, sample size, and appropriate chart type.

SPC checks are performed on a timely basis and out-of-control

conditions prompt corrective action as appropriate.

• SPC data is maintained, monitored, and used by t