special cause concern/improvement

[send2dan]

Hello,

There are several different rulebases available/published that define special cause variation.

With regards to this package, I'm trying to find the answer to the following statements:

1. Special cause improvement is defined as by the {NHSRplotthedots} package as...
2. Special cause concern is defined as by the {NHSRplotthedots} package as...

I can't seem to (easily) find this information in the R help files for this package, but I might be looking in the wrong place?

Best wishes,

Dan

[ThomUK]

Hi Dan,
Thanks for using the package, and for the feedback. Yes, this probably needs including in the documentation.

Points are special cause if any of the following criteria are satisfied:

• Any point beyond the dotted control limits.

• 2 out of the last 3 points are beyond 2sigma (ie. 2/3 of the way from mean to control limit). Only the 2 points meeting the criteria are highlighted.

• 7 or more points on one side of the mean. In this case all 7 qualifying points are highlighted (or more if it's more points).

Whether they are blue (improvement), orange (concern), or purple (neutral) depends on which way the "improvement_direction" argument is set in the ptd_spc() function call. Up good, down bad, etc.