R & R Statistic

The variation (error) contributed by both Gage Repeatability and Reproducibility:

where:

EV is the Equipment Variation, or Repeatability

AV is the Appraiser Variation, or Reproducibility

% R&R is calculated using the Total Variation (TV):

% R&R may also be calculated using the Part Tolerance:

where USL is the Upper Specification Limit and LSL is the Lower Specification Limit

The %R&R relative to process variation is interpreted differently than the %R&R to the allowable tolerance.

See also: Gage R&R Analysis

Learn more about the Quality Improvement principles and tools for process excellence in Six Sigma Demystified (2011, McGraw-Hill) by Paul Keller, or his online Green Belt certification course ($499).