Perhaps so. Saying it's "not possible" seems like an overly strong conclusion. For specific interventions, I think it might be possible to have open, blinded p

Perhaps so. Saying it's "not possible" seems like an overly strong conclusion. For specific interventions, I think it might be possible to have open, blinded participation. E.g. for supplements which may affect memory: - Participants sign up to buy a supplement which they know will be one of k generally safe supplements or a placebo - The specific supplement or placebo they receive it thompson sampled (or similar) from our bandit given data so far, and sent to them unlabeled - They're only able to receive their next bottle if they complete weekly tests or measurements The value prop is that you're probably buying a pretty good intervention, even if you don't know which one it is (and perhaps you're getting a discount subsidized by the minority of people who are paying for a placebo at any given time). For a number of questions related to exercise, people may fall into camps about their prior beliefs, and may self-sabotage if they're in treatment group that goes against their preferences but there isn't a clear thing to sell. E.g. which of a family of training schedules helps people reduce their 10k running time the most?