Isoplot vs. Gage R & R

The Isoplot is a mainly graphical technique that focuses on repeatability. The assumption behind this focus is that one person will be taking any measurements for studies required for problem solving or improvement.

A gage R&R is a combination of analytical/graphical techniques that consider both repeatability and reproducibility. The assumption here is different in that it is expected that numerous people may be responsible for making measurements in the course of monitoring/controlling a process.

 

Miner’s explanation is correct from a Shainin primary training perspective. But the “isoplot” is really a Youden plot and can be used to compare repeatability of a single appraiser or two appraisers or even multiple appraisers. One critical difference is that the number of repeated measurements is 2 with the Youden/isoplot method and is 3 with the common “R&R” method.

I have an explanation of the differences in my article “Statistical Alchemy” in the Resources tab. This article also contains many references for you to research. Miner also has a lot of details in his blogs.

 

That is true for a bias, linearity or stability study. It is not true for an R&R.

 

Hello Kyle. I have never heard that one before. What was the source of the comment? That’s usually a clue to its accuracy…

 

Miner is correct.

Perhaps it is the word ‘artifacts’. Units that have a known value - even with some measurement certainty are used bias, linearity and stability studies. Tehhe re not necessary for R&R studies. It is sufficient to use a calibrated measurement device

They are also necessary for some types of ‘attribute’ studies particularly those that focus on false acceptance and false reject rates such as sensitivity and specificity studies, method comparisons etc.

 

To explain the rationale behind our statements. When running studies on bias, linearity and stability, it is important to know the accuracy of the measurement device. This drives the necessity for 'artifacts' of known dimensions. However, an R&R study is not concerned with accuracy, but is concerned with precision, or measurement variation. Therefore, there is no need for 'artifacts' of known dimension, because it doesn't matter.

 

Very well explained Miner.
The source - or the ‘requirement’ - comes from the definition of the terms and teh purpose of the study designs…

 

So I am curious as well as to who told you that?