FDA_TrackerJim said:

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…

Thank you for spelling out the reasoning rather than just the conclusion.

Adding the clinical framing, because it changes how the question reads. The useful move here is to separate what is established from what is widely repeated. Those two sets overlap less than the confident tone of most write-ups suggests, and the second set is where nearly all the disagreement on this board comes from.

sophie_paris said:

The useful move here is to separate what is established from what is widely repeated.

Mine went the same way, slower. The detail I would add is minor and it is already implied above.

sophie_paris said:

The useful move here is to separate what is established from what is widely repeated.

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.

One concrete data point for the thread. Practical: whatever you change, write down the date and the reason. In three months the reason is what you will have forgotten, and the reason is what makes the record worth having.