Phase 2 SPC

PHASE 2 SPC METHODS (Variables control chart)
  • Montgomery p. 204
  • Done after Phase 1 methods find initial and eliminate assignable causes of special cause variation.
  • Use methods with more statistical power (EWMA, CUSUM, other) than X-bar and R for faster shift detection without inflating Type 1 error.
  • Discourage use of sensitizing rules (runs rules) in X-bar and R charts for shift detection of a stable process (Type 1 error).
  • Tolerance chart (or tier diagram)
Used for ongoing monitoring of a process (outputs and/or inputs) to ensure that any changes in process variation are identified and addressed quickly during ongoing production.

See also:  Phase 1 SPC