Crossover Design Sample Size

Hi all

I'm having trouble figuring out the sample size needed for a 2x2 crossover study. The population hasn't been studied yet so I don't have exact exploratory data to call on regarding anticipated effect sizes but the best fit would suggest a medium-large effect size.

I'm not particularly strong on stats though and have been informed not to use effect sizes to figure out the sample size. So I guess with no exploratory studies to replicate and if I'm not to use effect sizes, how do I figure out the sample size?

I don't think I can simply work it out based on the analysis I want to run because there may be ethical implications with using too many of my population at this stage of research.

Any ideas? Or signposts to papers?

Thank you :)


Less is more. Stay pure. Stay poor.
Nope you need effect sizes to guide the planning. You can also base sample size on precision estimates, but those still need to be anchor on an effect!