To force control limits and center line to be constantmain topic
To force control limits and center line to be constant1 In the control chart dialog box, click control chart Options. Click the Limits tab.
2 Under When subgroup sizes are unequal, calculate control limits, choose Assuming all subgroups have size, then enter a value. For example, enter a value of 6 to calculate the control limits and center line as if all subgroup sizes were 6.
3 Click OK.
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Note |
You should force the control limits and center line to be constant only when the difference in size between the largest and smallest subgroups is no more than 25%. For example, suppose the largest subgroup is size 125 and the smallest is 100. You can use this method because the size difference is 25% (125 / 100 = 25%). |