Adding the clinical framing, because it changes how the question reads. The version of this that has an answer is narrower than the version being asked. Narrow it and it becomes tractable; leave it broad and the thread will produce nine confident and incompatible replies.
Happy to go further on any of that.
Clinical perspective, offered as context rather than as advice. 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.
NurseLeah_Nash said: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.
Adding a me-too, because a thread of one person's experience is not much use. I had assumed I was the exception until I read this.
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Shop Reference StandardsNurseLeah_Nash said: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.
Adding the part of the answer the thread has not reached. 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.
Moderator note: two posts asking for a source have been merged into one. Please search the thread before asking again. No action needed from anybody.