SPC charts - control limits question

[Former Member]

Got a question about SPC charts:

When we display SPC Xbar charts, and let xmii set the control limits automatically, the chart does NOT calculate and show the control limits if any of the point values is null.

In other words - If I'm displaying an xbar chart, with point values 1,2,3,4,5 and let xmii calculate and show the control limits, it does.

But if my data is 1,2,3, null, 5 then it does NOT show the point for 4 and it also does NOT calculate and show the control limits on the whole graph.

Is this the way its designed? Is there a way we could work around it? Can we show points that are null?

Is there a way to have control limits calculated and shown even with nulls in the data output? Maybe we could specify that it should calculate control limits based on the values that are available and ignore the nulls.

Thank you

[jcgood25]

Have you tried suppressing the Null data point to exclude it from the calculations? It can still be shown in the resultset and have the cross-through indication on the datapoint marker.

Regards,

Jeremy