iSixSigma

Control Chart Wizard – Median And Range

Control Chart Suggestion

Median and Range

Control Chart Description

If the sample size is relatively small (e.g., less than 10-15) and the median is known, we can display how well a process is centered using the median or middle value. In contrast to the X-Bar and R control chart, this chart is useful when you would like to see less influence by data outliers. This can be an advantage or a disadvantage depending on your objective. The range of a sample is simply the difference between the largest and smallest observation. The Median and R control chart is used with continuous/variable data when subgroup or sample size is between 2 and 15.

Control Chart Formulae

Median and Range Control Chart Formulae
Table of Constants

Control Chart Example

Median and Moving Range Control Chart Example

Additional Resources

References

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

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