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.

TrialNerd_Beth 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. Posting only so the count is not one.

TrialNerd_Beth 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…

There is a second half to this that has not been said yet. There is a difference between no evidence and evidence of no effect, and this subject is one where the two get swapped freely in both directions.

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

Adding the numbers, since they settle part of this. Give anything pharmacological four weeks before you judge it, and give anything measured weekly a four-point rolling average before you call it a trend.

One thing that is still open after TrialNerd_Beth’s answer:

Was that from a primary source or from a summary of one?