From the other side of the consultation, briefly. Start from the measurement rather than the conclusion. Almost every disagreement here turns out to be two people measuring different things and comparing the numbers anyway.

hank_denver said:

One practical note: write down what you did and when, before you need it.

Adding the part of the answer the thread has not reached. 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.

One concrete data point for the thread. The boring version of this is the one that works, and the boring version is: measure a baseline, change one variable, wait, measure again under the same conditions. Nobody wants that answer and it is still the answer.

Correct me if the detail matters more than I have assumed.

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?

Moderator note: good thread. Keeping it here rather than moving it, because the question is general enough to be useful. Tagging this one for the weekly digest.