Control Chart Suggestion

Average And Standard Deviation – X-Bar and s

Control Chart Description

If the sample size is relatively large (e.g., greater than 10-15), the sample standard deviation (s, sigma or s) is a more efficient indicator of process variability. It is typically more difficult to calculate and is less sensitive in detecting special causes of variation that cause only a single value in a subgroup to be unusual. The average and standard deviation control chart is used with continuous/variable data when subgroup or sample size is greater than 10-15.

Control Chart Formulae

Average and Standard Deviation Control Chart Formulae
Table of Constants

Control Chart Example

Average and Standard Deviation Control Chart Example

Additional Resources


Wheeler, D.J., & Chambers, D.S. (1992). Understanding Statistical Process Control. Knoxville, TN: SPC Press.

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