There are very few times when you should start to investigate a process once you have established Statistical Process control (SPC), and the process is considered to be under control. What is the main reason you should investigate?
Question 17 options:
Behavior is normal
A single plot falls outside the control limits
A large number of plots are on or near the center line
3 out of six values are above the central line
There is no real trend in any direction
The main reason you should investigate is: There is no real trend in any direction.