Tools

Repeatability X-Bar Chart Calculations: Combined Appraisers

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 all Appraisers

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

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where

x-doublebar is the centerline

R-doublebar is the centerline of the Repeatability Range Chart

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

$images\conc2039_wmf.jpg$

where

x-doublebar is the centerline (above)

S-doublebar is the centerline of the Repeatability Sigma Chart

c4 is based on the sample size m = the number of trials and number of samples g = the number of Appraisers times the number of parts.

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