Dear Experts,
How can we know that the data have permanently moved away from the initial baseline?
Thanks

Dear Experts,
How can we know that the data have permanently moved away from the initial baseline?
Thanks

Use of a control chart will allow you to track the pattern of the process as well as identify trends and predict future trends. The baseline is set after a suitable amount of data is collected. If you notice a shift in the mean, your baseline has changed but there is really no way to know if the change is permanent. This is why trends and anomalies are investigated to determine the cause. If the cause is assignable, the process shift can be prevented and the baseline will remain the same.

If trends are allowed to go without investigation and correction, the process will probably show a change in the baseline. Remember that the change may or may not be permanent. If the process goes through set-up at a later date you may find the cause of the shift has been eliminated and the process may return to the original baseline on its own. Although this may sound like a good thing, it really isn't because you have not determined and eliminated the cause of the shift and it may happen again.

I hope after all that I understood your question and helped a bit. If not, feel free to restate the question.

Dave

Let me please ask a couple of questions.

What kind of data that measures what?

Now I will shoot from the hip, as the cliche goes. If you are using SPC, a gradual tightening or shifting of USL/LSL can lend a lot of confidence in departure from the baseline. However, nothing is permanent so a continued vigilance (with respect to the data's orientation against the original) is needed.