Posting this under the heading it deserves: Repeatability versus intermediate precision — what changed since Everything below is what sits behind that.
What changes if the standard account of Repeatability versus intermediate precision is wrong? I ask because I have been treating it as settled and I noticed this week that I could not say why.
Working through the consequences rather than the evidence, since others here are better placed on the evidence.
An independent laboratory's method being different from the supplier's is not a discrepancy. It becomes one only when the results differ by more than both methods' demonstrated precision.
Reporting the observation and leaving the explanation open deliberately.
Reporting a result to more decimal places than the method's precision supports is a small dishonesty that appears everywhere. A method with a two per cent relative standard deviation does not support a figure quoted to a hundredth.
I would treat the number as indicative rather than as a measurement.
This is the answer, and the reason it is the answer is the more useful part.
This follows post #3 rather than contradicting it.
Limits of detection and quantitation: LOD is the lowest concentration that produces a signal above background. LOQ is the lowest concentration at which the method meets precision and accuracy acceptance criteria. Both are determined empirically.
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