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Process
Sigma based on Range Chart
The process sigma of the
subgroups.
Note: This is the standard
deviation of the observations, NOT the standard deviation of the subgroup
averages, which is calculated by dividing the standard deviation of the
observations by the square root of n (the subgroup size).
(n = constant) , OR
(n 
constant)
where:
- Rj is the Subgroup
Range of subgroup j >
- R-bar is the Average
Range
- m is the total number
of subgroups included in the analysis
- d2 is a function
of n (available in any statistical quality control textbook)
- ej and fj are Burr's
constants (Burr, 1969)
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