During PQ phase 3 data assessment to set up the 3 tier control system (Alert/Action/Specification), we calculated a high standard deviation (Sigma). Therefore, while setting up 3 tier control (Alert Level=Average + 2 Sigma; Action Level: Average + 3 sigma) we found the action level is too high (even exceeds the Specification).
Can anyone advise how we can handle such situation? Is there anyway we can handle the spike data that leads to a high value of Sigma?
Thanks in anticipation.