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. I would put this at better than even and not much better.
Washout with a one-week half-life: the arithmetic — does this still hold? — that is the question, and I have not found it answered plainly anywhere I have looked.
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.
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.
I would put this at better than even and not much better.
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.
Post #5 is the version of this I will quote in future. One addition.
Order effects matter. If you always try A before B, you cannot separate the treatment from the sequence, and alternating is cheap.
I have said this before in a thread nobody could find, so it is worth repeating.
It does not tell you about anybody else, which is why aggregating these accounts does not produce evidence of the kind people want it to.
I have deliberately not rounded that, because the rounding is where the argument starts.
Answering the question post #6 raises rather than the one it answers.
The useful distinction on Washout is between what was measured and what was inferred from it. Both end up in the same sentence and only one of them has error bars.
Worth separating Washout as a question about the compound from Washout as a question about the documentation. They get answered by different people and only one of them is answerable here.
Post #10 answers the question as asked. The question underneath it is different.
Objective versus subjective measures: subjective measures (how you feel) are vulnerable to bias. Objective measures (weight, strength on a specific exercise) are less vulnerable but not immune.
That is where I would start, not where I would stop.
The question underneath Washout is usually "how would I tell?" rather than "what is true?", and that one has a method attached to it.
Write down what you would expect to see under each hypothesis before you collect anything. If they predict the same observation, collecting it will not help.
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.
I am aware this is the third time this month I have made this point.
Coming back to post #13, because the follow-up matters more than the original answer.
Before the thread moves on from Washout — what is the sample size behind the claim? I am not being difficult; I have seen the same figure quoted from an n of four and from an n of four hundred.
Post #13 is right about the mechanism and I think understates the practical bit.
Two things can be true about Washout at once: the mechanism is plausible and the evidence for the size of the effect is thin. Most of the argument here is people defending the first against attacks on the second.
Sample size in n-of-1: you are the sample. Repeated measurements (weekly weighings, daily mood scores) increase the power to detect a real effect even though n=1.
Noting that I have skin in this question and have tried to discount for it.
Sensible. I would want the same detail before I acted on it either.
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.
Multiple outcomes measured without a primary one means something will move. Nominate the primary in advance and report the rest as secondary.
That is the version I would defend. It is not the version I started with.
A photograph or a device reading is a harder record than a recollection, and where one is available it should be the record.
The literature is thinner on this than the confidence in the thread implies.
Generalisability: a robust n-of-1 result applies to you. It does not tell you much about whether the effect generalises to others similar to you, much less to people different from you.
It took me longer than it should have to see that.
I had written a reply contradicting post #24 and deleted it. Here is what survived.
Reporting rather than recommending, on Washout. What happened is above. Whether it should have is a different question and not one I am qualified to answer.
Picking up post #26: that is the part I would want checked first.
Checked the Washout claim against the primary source this morning. It survives, with a narrower scope than the version quoted here. Posting the narrower scope.
Narrowing post #26, because the general version has more than one answer.
Offering a way to settle Washout rather than another opinion about it. Two measurements, taken the same way, a fortnight apart. If the difference is within the noise, the question was not answerable at this precision.
Everything in post #28 holds. The case it does not cover is the one I have.
Second-hand on Washout, so weight it accordingly — someone whose method I trust told me this and I have not verified it myself.