Research Methods · N-of-1 designs

Designing a personal experiment that could change your mind

Research Methods › N-of-1 designs confounding worked example data table effect size

m.guerreroTL28 Jan 2026#1

Posting this under the heading it deserves: Designing a personal experiment that could change your mind Everything below is what sits behind that.

I was wrong about designing a personal experiment in a thread last spring and I would like to correct it publicly rather than quietly.

The error was in the units, which changed the conclusion by an order of magnitude. Setting out the corrected version, and the way I now check for that class of mistake.

0 likes 7mo

e.coelhoTL213 Jan 2026#2

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.

0 likes 6mo

f.abrahamsenTL2Member17 Jan 2026#3

Record everything that changed, not just the intervention. Personal experiments are confounded by life, and the confounders are only recoverable if they were written down.

That matches what I was told, which is not the same as knowing it.

8 likes 6mo

ca.haddadTL220 Jan 2026#4

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.

Not the whole picture, but the part of it I can speak to.

19 likes 6mo

GDashwoodTL3Regular24 Jan 2026#5

ca.haddad, post #4: 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. Not the whole picture, but the part of it I can speak to. Go to post

Taking post #4 at face value and following it one step further.

The interesting personal experiments are the ones where the answer was no. They are also the ones least likely to be written up.

Noting that I have skin in this question and have tried to discount for it.

27 likes in reply to #4 6mo

m.yilmazTL227 Jan 2026#6

m.guerrero, post #1: Posting this under the heading it deserves: Designing a personal experiment that could change your mind Everything below is what sits behind that. I was wrong about designing a personal experiment in a thread last spring and I would like to correct it publicly rather than quietly. The error was in the units, which changed the conclusion… Go to post

Post #2 and I disagree about the size of the effect, not about the direction.

Duration should be set by how long an effect would take to appear rather than by patience. Stopping early is the commonest reason a personal experiment answers nothing.

0 likes in reply to #1 6mo

g.ibarraTL230 Jan 2026 · edited#7

Nothing in a personal experiment is medical advice to anyone including yourself, and several people here have found that a prescriber will happily discuss a well-documented one.

5 likes 6mo

This topic was referenced in

An ABAB design with a data table and honest limitationsResearch Methods › N-of-1 designs · 2 replies

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