Rob,
“When plotting control charts in Minitab, Test 2 = 9 points in a row on same side of center line.”
This is the only part of your post that is strictly true.
The presence of this pattern suggests that there is sufficient evidence of a special cause to warrant investigation. That is; it is economic when the signal appears to try and find out why. That is the meaning of all the tests.
So, if you can fnd the special cause and institute it into the process, than an improvement might be possible.
The part about above the center line and below is situational. What if above the center line is in the direction of defective parts? Larger is not always better.
The presence of any signal on test 2 will indicate a process improvement possibility. If in the direction of goodness, institutionalize it in the process. If it is in the direction of badness, find a way to prevent it ever happening again.
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