Define the Data Points Used to Calculate Control Chart Limits

It's Easy to Set or Fix Limits in QI Macros Control Charts

When you create a control chart using QI Macros, the data you select is the baseline data. It is used to calculate the control limits. If you selected 20 points, 20 points are used. If you selected 14 points, then 14 points are used and so on. When you add data to an existing chart, the limits stay the same.

If you want to change the data points used to calculate the control limits after you have added new data:

  • use Recalculate UCL /LCL to use ALL of the data points.
  • use Fix Control Limits to use a subset of the data points.

Here's how to use the Fix Control Limits option:

  1. Click on the last point you want to include in the fixed control limit calculations:

  2. Click on the QI Macros Chart menu > Process Changes, and then select "Fix Control Limits":

  3. QI Macros will use the selected point to calculate the fixed control limits:

    set or lock control limits
  4. Your chart will now indicate where the Fixed Control Limits point is, as the centerline up to and including the point you selected, will be dashed. Please note that the centerline to the right of your point will remain solid:


  5. Don't forget to click on Analyze Stability to  rerun stability analysis using the new control limits:
  6. qi-macros-chart-menu

Learn More...

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