If your cycle is 7 days (which it isn't, but which I initially understood it to be), you will want to make sure that, with an experiment running for 2N weeks, you take the LSD-spiked water exactly N times on Monday and N times on Thursday, rather than relying on luck to get close to that.
One way to do that is to make 2N packages containing a spiked and a non-spiked sample, with one sample marked 'take me first', and, in N cases, have the LSD-spiked sample be that sample. Of course, if you do that, it is even more important to not inform the subject about the history of he experiment before it is over.
> If your cycle is 7 days (which it isn't, but which I initially understood it to be), you will want to make sure that, with an experiment running for 2N weeks, you take the LSD-spiked water exactly N times on Monday and N times on Thursday, rather than relying on luck to get close to that.
I see. So you were suggesting throwing in a categorical variable for the day of week and including that as a additive covariate to control for fixed-effects on days. I haven't actually run into any of my experiments depending on day of week to any important degree, but I still try to avoid 7-day blocks to make that less of an issue. It's not like there's usually an advantage to running in a weekly block, so better safe than sorry.
One way to do that is to make 2N packages containing a spiked and a non-spiked sample, with one sample marked 'take me first', and, in N cases, have the LSD-spiked sample be that sample. Of course, if you do that, it is even more important to not inform the subject about the history of he experiment before it is over.