Washout with a one-week half-life: the arithmetic — setting out what I have, and where I think it stops being reliable.
Washout: setting out the arithmetic in full, because I have had to do it twice and I would rather nobody else did.
Every step is shown. If the answer is wrong the error will be visible, which is the point of writing it out rather than posting the result.
A washout period between conditions is what stops one bleeding into the next, and its length should be set by the half-life rather than by convenience.
On washout: the maintained page in the documentation commons covers the general case with citations and a review date, which is more reliable than any reply here including this one.
Coming back to post #3, because the follow-up matters more than the original answer.
The reason washout keeps being re-asked is that the answer is conditional and people quote it without the condition. It is not that the answer is unknown.
Post #3 is right about the mechanism and I think understates the practical bit.
A rolling mean over several days is far more informative than any single reading for anything that varies day to day, which is nearly everything.
Scoping that to what I have actually seen rather than what I have read.
What I would want before treating washout as settled: the method, the sample, and whether anyone tried to find the opposite result. Two of the three are usually missing.
Agreed on all of that, and I have nothing to add to it.
Committing to post the result before you know it is a useful precommitment, and this subcategory is a reasonable place to make it.
The part I am sure of is shorter than the part I have written.
One caution on washout: everything above assumes the underlying documentation is what it claims to be. That assumption is doing real work and is rarely stated.
A photograph or a device reading is a harder record than a recollection, and where one is available it should be the record.
Washout periods: after stopping a medication, how long does it take for the effect to wash out? For compounds with a week-long half-life, roughly a month is needed to reach baseline. Using that washout period in a before-after design strengthens the inference.
Narrowing post #16, because the general version has more than one answer.
Filing a mild objection to the consensus on washout. Mild because I might be wrong; an objection because nobody has addressed the case that does not fit.
Everything in post #14 holds. The case it does not cover is the one I have.
Washout was covered in the wiki last year and the page has a review date on it, which is a better starting point than my memory of a thread.
Post #19 put the caveat in the right place and I want to underline it.
Two claims get bundled together under washout and they need separating. The descriptive one — this is what was observed — is usually well supported. The causal one — this is why — usually is not.
Almost every disagreement in threads like this one dissolves once you say which of the two you are making.
Building on post #19 rather than restating it.
Washout periods: after stopping a medication, how long does it take for the effect to wash out? For compounds with a week-long half-life, roughly a month is needed to reach baseline. Using that washout period in a before-after design strengthens the inference.
The most useful thing anyone has posted about washout in this category was a table of what had been measured and by whom. That is what I would want again.
Multiple outcomes measured without a primary one means something will move. Nominate the primary in advance and report the rest as secondary.
Happy to be corrected if someone holds better data than mine.
A washout period between conditions is what stops one bleeding into the next, and its length should be set by the half-life rather than by convenience.
It reads as pedantry until the day it does not.
Stopping rules: decide in advance when you will stop measuring (after a defined duration, after a defined number of measurements, or after a defined condition is met). Not deciding in advance means stopping when the result satisfies you, which is bias.
Not the answer, but possibly the question that gets there.
I disagree with the framing of washout above, and I think it is a substantive disagreement rather than a terminological one. Setting out why, so it can be checked.
The reasoning depends on an assumption that is doing a lot of work and is never stated. If the assumption holds, the conclusion follows. I do not think it holds generally.