Repeatability X-Bar Chart Calculations: Per Appraiser

Plotted Statistic

the average of the trials for each part for each Appraiser

Center Line (x-doublebar):

the grand average of all the trials for all parts for each Appraiser (i.e. a different Center Line is calculated for each Appraiser).

UCL , LCL (Upper and Lower Control Limit) based on Range Chart calculations (2 ≤ Number of Trials ≤ 10)

where

x-doublebaroper is the centerline for the given Appraiser

R-baroper is the centerline of the Repeatability Range Chart for the given Appraiser

d2* is based on the sample size m = the number of trials and number of samples g = the number of parts

Notes:

1. Some authors, including AIAG, refer to the quantity (3 / d2*(SQRT(#trials))) as A2

2. Table for d2* values may be found in A.J. Duncan, Quality Control and Industrial Statistics, 1965, Third Edition Richard D. Irwin, Homewood, Illinois. Table D3, pg. 910.

UCL , LCL (Upper and Lower Control Limit), based on Sigma Chart calculations (Number of Trials > 10)

where

x-doublebaroper is the centerline (above) for the given Appraiser

S-baroper is the centerline of the Repeatability Sigma Chart for the given Appraiser

c4 is based on the sample size n = the number of trials.

Notes: Some authors, including AIAG, refer to the quantity (3 / c4*(SQRT(#trials))) as A3.

See also:

Repeatability X-Bar Chart Calculations: Combined Appraisers

Repeatability Range Chart Calculations: Combined Appraisers (If (2 ≤ Number of Trials ≤ 10)

Repeatability Sigma Chart Calculations: Combined Appraisers (If (Number of Trials > 10)

Repeatability Range Chart Calculations: Per Appraiser (If (2 ≤ Number of Trials ≤ 10)

Repeatability Sigma Chart Calculations: Per Appraiser (If (Number of Trials > 10)

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).