Section 7 CUSUM Charts
Lesson S07-03
Text: Section 7 page 11
Duration: 5 minutes
Design Considerations for h and k
The specification of H (and h) was briefly described earlier. H refers to the value of the control limit on a CUSUM chart. It is common to indicate the control limit by specifying h which is the number of standard deviations the control limit should be placed at. Common values for h are 4 or 5. MINITAB defaults to h = 4. While reducing h can minimize Type II errors (probability of failing to detect a significant shift), it will also lead for more Type I errors (incorrectly concluding that the process is out of control when it isn’t).
The reference value or slack (K) was discussed earlier. K is typically chosen to be halfway between the target and the mean we wish to detect. That is, K is half of the magnitude of the shift. k is the number of sigma’s that make up K.
An Additional Resource – White Paper
Whitepaper: What is a CUSUM Chart and When Should I Use One?
The full list of Integral Concepts whitepapers.
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