How to alternate intervention - every other day? Every other week?

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Pretty basic question, but I don’t think the Getting Started quite covers it.

Let’s say you want to test what an intervention (like eating kiwis or taking a pill) does to your sleep. You’ve got your lifestyle mostly constant (thanks Covid), now you just need to schedule the intervention. Blinding yourself is impossible (fake kiwis anyone?).

What are the pros and cos of,

  • test the intervention Every Other Day
  • test the intervention one week on, one week off

These two frequencies were chose to overlap with common human activity rhythms. Might there be better ones?

I’m thinking that EOD might be confused by other factors, such going to the gym every other day. On the other hand, testing the intervention for a week straight on, might lead to tolerance effects.

I’ve mostly used “always off, then months on” frequencies. Anyone suggestions?

These experiment design questions can be unexpectedly tricky to answer. Some of the issues you want to consider will require domain knowledge:

  • What do you expect are the cumulative effects?
  • What’s your guess about a washout period?
  • How difficult is the intervention to prepare and execute?
  • Are there costs of stopping? (For instance, stopping coffee can induce withdrawal effects.)

Are you literally thinking about testing Kiwis? Or was this just a placeholder?

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Definitely don’t do Every Other Day: If you are going to test something that you expect to have an immediate, non-cumulative effect (e.g. the effect of caffeine on sleep), randomize your days!