Variation and Uncertainty - Communicating Data with Tableau - page 133

Figure 7-14. Creating Shewhart's control limits via calculated fields
Add these three new calculated fields to the level of Detail for All Marks, and use them to
create three new reference lines: UCL and LCL in the top Individuals chart, and MR_UCL in
the bottom Moving Range chart.
Create two new Calculated Fields for the signals, one called Signals (to be used in the top
Individuals chart) and the other called MR_Signals (to be used in the bottom Moving Range
chart) by copying and pasting the equations available in Signals.doc and MR_Signals.doc .
You can also find these files to download at http://dataremixed.com/books/cdwt .
Drag these new calculated fields to their respective Colors shelves— Signals should be
placed on the Individuals Circle Color shelf and MR_Signals should be placed on the Mov-
ing Range Circle Color shelf.