ABAB design: I have looked for the primary source twice and failed twice. Either it does not exist or it is somewhere I do not know to look, and I would like to know which.
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Research Methods · N-of-1 designs · continued
An ABAB design with a data table and honest limitations — a second dataset posts 91–119
This is a continuation of a long topic, addressed by post number rather than by page. Start at post 1 · go to the accepted answer.
A single-person experiment can be genuinely informative if it has a pre-specified outcome, a defined period, and a plan written before the data arrives. Most accounts here have none of those.
It is a small point and it changes the answer, which is an awkward combination.
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t.demir, post #56: Post #54 answers the question as asked. The question underneath it is different. 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. I would put the burden of proof on the interesting explanation, not the dull one. Go to post
On ABAB design the community has more anecdote than the confidence in this thread implies, and I include my own contribution in that.
Post #91 answers the question as asked. The question underneath it is different.
ABAB design looks different depending on whether you are reading the primary literature or the summaries of it, and the difference is not in our favour.
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Post #91 put the caveat in the right place and I want to underline it.
Order effects matter. If you always try A before B, you cannot separate the treatment from the sequence, and alternating is cheap.
If anyone can point at the primary source I would be grateful.
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m.yildiz, post #79: I would keep ABAB design and the decision it usually gets used for separate in this thread. They are related and they are not the same question, and merging them is why the last one went badly. Go to post
Where I would push back on the ABAB design consensus is the confidence, not the direction. The direction looks right. The confidence is borrowed.
baseline_table, post #49: Order effects matter. If you always try A before B, you cannot separate the treatment from the sequence, and alternating is cheap. Posting it because the silence on this was starting to look like agreement. Go to post
Blinding yourself is harder than it sounds and is not impossible. Somebody else preparing labelled containers is the usual approach and it requires a second person you trust.
This has been discussed before and I could not find the thread, so, again.
Where I part company with post #95, and it is a narrow parting.
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.
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first_vial, post #72: ABAB design is a good example of a question where the honest answer is boring and the interesting answers are unsupported. I would go with boring. Go to post
Post #99 is the version of this I will quote in future. One addition.
Filing a mild objection to the consensus on ABAB design. Mild because I might be wrong; an objection because nobody has addressed the case that does not fit.
s.lindqvist, post #77: 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. That is what I would do. It may not be what is correct. Go to post
Multiple outcomes measured without a primary one means something will move. Nominate the primary in advance and report the rest as secondary.
The literature is thinner on this than the confidence in the thread implies.
t.ndiaye, post #55: Saving this. It is the version I will quote when the question comes round again. Go to post
Reporting the whole series rather than the interesting segment is the discipline that makes personal data worth reading. Selective reporting is the default without effort.
If this contradicts something upthread, the upthread version may well be the better one.
The arithmetic in post #103 is right; the assumption feeding it is the part to check.
Worth separating ABAB design as a question about the compound from ABAB design as a question about the documentation. They get answered by different people and only one of them is answerable here.
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i.aranda_es, post #91: ABAB design: I have looked for the primary source twice and failed twice. Either it does not exist or it is somewhere I do not know to look, and I would like to know which. Go to post
Where I part company with post #103, and it is a narrow parting.
When to run an n-of-1: this design works when you want to know whether a treatment works for you, not whether it works in general. For that purpose, it is efficient.
No disagreement from me. Posting only so the question does not look ignored.
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I would put moderate confidence on the mainstream reading of ABAB design and no more. That is not scepticism for its own sake; it is where the sourcing actually stops.
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m.duarte, post #106: Statistical analysis of n-of-1 data: comparing before versus after with a t-test or similar is one approach. Plotting the data visually is another. Both are valid. Not the whole picture, but the part of it I can speak to. Go to post
Measure the same thing the same way at the same time of day. Most of the noise in personal data is measurement protocol rather than biology.
Confirming post #108 from a second method, which matters more than confirming it from a second person.
Practical note on ABAB design: write down what you expect before you look. The number of times I have found what I went looking for is higher than chance would allow.
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trough_index, post #51: My understanding of ABAB design is a few years old and may have been superseded. If it has been, I would genuinely like to know rather than keep repeating it. Go to post
Building on post #110 rather than restating it.
A single-person experiment can be genuinely informative if it has a pre-specified outcome, a defined period, and a plan written before the data arrives. Most accounts here have none of those.
figure_review, post #76: Confirming post #74 from a second method, which matters more than confirming it from a second person. The best thing about this subcategory is that people post their protocols before their results. That order is what keeps it honest. Go to post
Post #113 put the caveat in the right place and I want to underline it.
Withdrawal and reintroduction is the strongest design available to an individual, and it only works for effects that reverse on a timescale you can observe.
micrograms, post #40: Speaking only to ABAB design as I have actually seen it, rather than as it is usually described: the effect is real, it is smaller than the thread suggests, and the variance between people is larger than the effect. Go to post
Taking post #114 at face value and following it one step further.
Expectation effects in an unblinded self-experiment are large and are not a character flaw. Knowing what you expect to find is a reason to design against it.
None of the above is medical advice and I am not qualified to give any.
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