Dr.BariatricHTX said:

Worth answering the question that was asked rather than the one behind it.

Coming at Dr.BariatricHTX’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.

Adding the numbers, since they settle part of this. 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.

I would rather be corrected than agreed with, if it comes to it.

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

How would you tell the difference between that and the alternative explanation?

bri_stats said:

One habit that pays for itself: post the method alongside the number.

This is where I part company with the consensus forming above. The counter-case has not been addressed. Somebody upthread described the situation that does not fit, and the thread moved on rather than engaging with it, which is the failure mode this board is supposed to avoid.

bri_stats said:

One habit that pays for itself: post the method alongside the number.

Correct as far as it goes. The part it does not cover is what to do when the honest answer is "not enough data", which is more often than anyone likes.