Adding the clinical framing, because it changes how the question reads. 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.

That is the short version; the long version is somebody else's post.

BiostatsBrad said:

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

Coming at BiostatsBrad’s question from a different direction. The mechanism and the magnitude are separate questions. Agreeing that something happens says nothing about whether it happens enough to act on.

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

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.

Happy to go further on any of that.

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

What would you measure differently if you were starting again?

Moderator note: leaving this open. It is being argued well and the disagreement is the useful part. Tagging this one for the weekly digest.