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Please bear with me, it's been a while since I actually statisticed.
I'm setting up X-MR charts for a chemical process (extracting a protein from a biological source), whereby certain characteristics are sampled from a finished batch. The business goal is to automatically plot based on the results of our finished goods. We have a data visualization tool that publishes the charts, and can send email alerts for certain conditions (i.e. a rule is violated). So I'm using Excel to put formulas in to perform the control chart tests, which then gets vacuumed into our data visualization tool.
In searching for web literature, I found these posts, which independently (or maybe dependently, although sources aren't cited) call for the same tests on MR charts.
Using tests for special causes in control charts - Minitab
Applying the Out of Control Tests | BPI Consulting (spcforexcel.com)
Since MR is by definition the absolute value of the change, what does 6 (or 7) points increasing/decreasing indicate is actually happening with the process? Same with the 14 points alternating up and down. As I wrestle with it mentally, I'm struggling with how this test is relevant when directional indication (the +/- sign) is removed.
I'm setting up X-MR charts for a chemical process (extracting a protein from a biological source), whereby certain characteristics are sampled from a finished batch. The business goal is to automatically plot based on the results of our finished goods. We have a data visualization tool that publishes the charts, and can send email alerts for certain conditions (i.e. a rule is violated). So I'm using Excel to put formulas in to perform the control chart tests, which then gets vacuumed into our data visualization tool.
In searching for web literature, I found these posts, which independently (or maybe dependently, although sources aren't cited) call for the same tests on MR charts.
Using tests for special causes in control charts - Minitab
Applying the Out of Control Tests | BPI Consulting (spcforexcel.com)
Since MR is by definition the absolute value of the change, what does 6 (or 7) points increasing/decreasing indicate is actually happening with the process? Same with the 14 points alternating up and down. As I wrestle with it mentally, I'm struggling with how this test is relevant when directional indication (the +/- sign) is removed.