Specificity, linearity, accuracy, precision, range, robustness — with real criteria

The opening post is right about the mechanism and I think understates the practical bit.

My position on specificity is current rather than settled. I have revised it once already and I expect to again, so treat it accordingly.

Clear enough that I do not think I have a follow-up, which is unusual.

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.

It took me longer than it should have to see that.

The honest answer on specificity is that it depends, and the useful part is the list of what it depends on. Four items, in rough order of how much they matter.

Most people get the first two right and then argue about the fourth.

A method that reports the same number for every lot is worth a second look. Real processes vary, and a total absence of variation is a statement about the measurement rather than the process.

Following this. I have the same question and no better information than the first post.

Robustness testing deliberately varies the parameters most likely to drift — organic percentage, pH, temperature, flow — and shows the result does not. It is the part of validation that predicts whether a method will transfer.