Dr.PainCLE 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.

There is a second half to this that has not been said yet. 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.

Following on from Dr.PainCLE — and this may be the naive question:

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

josh_phd_bmore said:

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

I read this differently from josh_phd_bmore, on substance rather than tone. This treats a plausible mechanism as a demonstrated one. Plausible is where you start looking, not where you stop.

josh_phd_bmore said:

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

That is right, and it stops being right at the edges. The general case is well behaved; the interesting cases in this thread are all at the boundary where the general case breaks.