PharmacoVig_BOS said:

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

I read this differently from PharmacoVig_BOS, on substance rather than tone. I think the framing smuggles in the conclusion. Ask it the other way round and the obvious answer reverses, which usually means the question is doing the work.

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

PharmacoVig_BOS said:

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

Agreeing with PharmacoVig_BOS, and the qualification matters more than the agreement. One addition: an unstated method makes a report close to uninterpretable. "99% pure" without the technique, the standard and the conditions is a claim, not a measurement.

PharmacoVig_BOS said:

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

That reframing is the part I needed. Taking it to my next appointment.

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.

Worth separating that from certificates of analysis, which this thread keeps folding into the same question. They behave differently and the advice does not transfer.

Dr.NateNeph said:

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…

Same pattern here, and in the same order. The detail I would add is minor and it is already implied above.