From the other side of the consultation, briefly. 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.

Happy to go further on any of that.

DanielChem_CHI said:

If you are going to change something, change one thing and give it long enough to express itself.

Coming at DanielChem_CHI’s question from a different direction. 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.

One concrete data point for the thread. One habit that pays for itself: post the method alongside the number. A figure without its method cannot be checked, and an unchecked figure is how this community accumulates folklore.

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

Following on from DanielChem_CHI — and this may be the naive question:

How long did you give it before you decided it was working?

Moderator note: a couple of off-topic posts removed. Report rather than reply if it drifts again.