Statistical Power estimation for fixed effects panel model?

[Brad Anderson]

This is not Stata specific and may not be an appropriate question. If so moderators please delete. I've been asked to provide power estimates in support of a grant application. There will be 28 days of data on n subjects. There are 3 predictors and a pure within subject design is appropriate. Complicating this is that a X1 by X2 by X3 interaction effect is hypothesized. At this point, I don't even have guestimates of effect sizes, but even if I did I don't really know where to start in terms of estimating sample size requirements. I'd be most appreciative if anyone could offer any suggestions as to how to approach this. Thanks much.

[Carlo Lazzaro]

Brad:
perhaps this old Stata thread can shed some light on the topic you're interested in: https://www.stata.com/statalist/arch.../msg00193.html

[Brad Anderson]

Thanks Carlo, unfortunately, the link doesn't work. Might just be my system, I work in a hospital and things are pretty locked down.

[Carlo Lazzaro]

Brad:
it works for me; just clicking on the link points me to the related Stata thread.

[Brad Anderson]

Thanks again Carlo, works for me too when I logged in using a non-intitutionalized computer. I will take a look at powercal.

[Carlo Lazzaro]

Brad:
thanks for letting us know.