stefan_berlin 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…

I read this differently from stefan_berlin, on substance rather than tone. 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.

stefan_berlin 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…

That is right for the common case. Whether it is right for the case being asked about depends on a detail that has not been given.

stefan_berlin 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.

Clinical perspective, offered as context rather than as advice. It helps to say which part of this you are uncertain about. A precise question gets a precise answer; a general one gets everybody’s favourite anecdote.

Closing the loop on my own question.

Closing the loop. The answer turned out to depend on the detail I had left out of the opening post, which is a lesson about how to ask rather than about the subject.