labquiet_amy 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. The confidence in this thread is running ahead of the evidence, and I would rather the uncertainty were stated than smoothed over because it is unsatisfying.

labquiet_amy 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…

labquiet_amy has the substance of this right. The condition it depends on is worth stating. Yes, and the corollary is less popular: if the reasoning holds, it also holds where it produces an answer we do not like.

If somebody has the primary source to hand I would rather cite it than paraphrase it.

labquiet_amy 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…

Bookmarking. The distinction being drawn above is the one nobody else makes. Printing the relevant bit and taking it with me.

Clinical perspective, offered as context rather than as advice. Whatever the answer turns out to be, the method for getting there is the same: state the assumption, do the arithmetic in public, and invite the correction. That is slower than asserting, and it is the only version that survives being wrong.

Reporting back.

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.