Understanding peptide purity percentages — what worked for you?

anna.melb_AU said:

There is a difference between no evidence and evidence of no effect, and this subject is one where the two get swapped freely in both directions.

Adding the part of the answer the thread has not reached. Order of operations matters more than any single choice here: establish a baseline, change one thing, wait long enough for it to express itself, then measure again under the same conditions.

Adding the numbers, since they settle part of this. If you are comparing against somebody else’s result, check that you are comparing the same measurement taken the same way. Most of the apparent contradictions in these threads dissolve at that step.

A narrower follow-up, since the general answer is now clear:

What did you change at the same time, and can you separate the two now?

lisa_labSD said:

If you are comparing against somebody else’s result, check that you are comparing the same measurement taken the same way.

Pushing back on lisa_labSD here. I think the framing smuggles in the conclusion. Ask it the other way round and the obvious answer reverses, which usually means the question is doing the work.

lisa_labSD said:

If you are comparing against somebody else’s result, check that you are comparing the same measurement taken the same way.

That holds where the measurement is reliable. Where it is noisy — and a lot of what gets tracked here is noisy — the same reasoning produces confident nonsense.

If somebody has the primary source to hand I would rather cite it than paraphrase it.