Lower Control Limit of Test-Retest Plot in MSAHello All,
I had a statistical interpretation question. I had run a few MSA studies and was interested in explaining or interpreting the results of the Test-Retest plot.
The definition that I find on the JMP website is
"Test-Retest Error
Indicates measurement variation or repeatability (also known as within error or pure error)."
In most cases, my data points are within the control limits and when I have a data point outside the upper control limit I believe I understand that that means this operator is measuring with higher variability (lower repeatability) compared to the rest.
However, the one that I am having a bit more trouble explaining to myself is if an operator's measurements are outside the lower limit. Is that a bad thing? Does this not signify that their overall repeatability is quite good, yet it is still marked red. Does it make sense to have a lower limit or am I missing something in the explanation?
Below is an example of my result. The control limits have different width as some of the group sizes are slightly different due to the nature of the experiment.
Any help is appreciated.
Advanced Statistical ModelingQuality and Process EngineeringWindowsRe: Lower Control Limit of Test-Retest Plot in MSAUnfortunately I don't see how the data was acquired? In other words, it is not clear what the rational subgroup is. In most measurement studies, the operator is between subgroup and therefore cannot possible affect the range (or stand deviation) chart. You need to understand what components of variation are captured within subgroup. Those are the only possible explanations for points outside control limits on the range/std dev chart.
Also, you should understand, points outside the control limits on the range/std dev charts are indications of inconsistency/instability due to the sources of variation changing within subgroup. Points outside control limits have nothing to do with "good/bad."
