Modify the control limits for G Chart

Stat > Control Charts > Rare Event Charts > G > G Chart Options > Limits

Display additional percentile limits at

In These percentiles of the distribution, enter one or more values to display additional percentile limits on your control chart.

Values that you enter affect only the line position on the control chart, not the test results.
Default control limits
Additional percentile limits at the 25th and 75th percentile

Place bounds on control limits

You can specify a lower bound and an upper bound for the control limits. If the calculated control limit is farther from the center line than the value that you specify, Minitab displays the bound instead of the control limit. Minitab labels the lower bound as LB and the upper bound as UB.


Upper bounds and lower bounds do not affect the calculations for any of the tests for special causes.