Repeatability Range Chart Calculations: Per Appraiser

Note: This chart is used when (2 ≤ Number of Trials ≤ 10)

Plotted Statistic:

The difference between the largest and smallest trial for each part for each Appraiser.

Center Line:

The Average Range for the parts from each Appraiser (i.e. a different Center Line is calculated for each Appraiser).

UCL , LCL (Upper and Lower Control Limit)

Separate Control Limits are calculated for each Appraiser:

where:

R-baroper is the Center Line (above)

d3 is based on subgroup size equal to the number of trials

d2* is based on a subgroup 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 (1+3(d3 / d2*)) as D4 , and (1-3(d3 / d2*)) )) as D3

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.

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 X-Bar Chart Calculations: Per Appraiser

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).