> On Aug 26, 2019, at 6:24 AM, CHATTON Anne via R-help <r-help@r-project.org> > wrote: > > Hello everybody, > > I am trying to accommodate the R codes provided by Donohue for sample size > calculation in the package "longpower" with lmmpower function to estimate the > post-hoc power (asked by a reviewer) of a binary GEE model with a three-way > interaction (time x condition x continuous predictor) given a fixed sample > size. In other words instead of the sample size I would like to estimate the > power of my study. > > Could anyone please help me to modify these codes as to obtain the power I'm > looking for. > > I would really appreciate receiving any feedback on this subject. > > Yours sincerely, > > Anne
Hi, Three comments: 1. Don't calculate post hoc power. Do a Google search and you will find a plethora of papers and discussions on why not, including these: The Abuse of Power: The Pervasive Fallacy of Power Calculations for Data Analysis The American Statistician, February 2001, Vol. 55, No. 1 https://www.vims.edu/people/hoenig_jm/pubs/hoenig2.pdf Post Hoc Power: Tables and Commentary https://stat.uiowa.edu/sites/stat.uiowa.edu/files/techrep/tr378.pdf Observed power, and what to do if your editor asks for post-hoc power analyses http://daniellakens.blogspot.com/2014/12/observed-power-and-what-to-do-if-your.html Retraction Watch: Statisticians clamor for retraction of paper by Harvard researchers they say uses a “nonsense statistic” https://retractionwatch.com/2019/06/19/statisticians-clamor-for-retraction-of-paper-by-harvard-researchers-they-say-uses-a-nonsense-statistic/ PubPeer Comments on the paper cited in the above RW post: https://pubpeer.com/publications/4399282A80691D9421B497E8316CF6 A discussion on Frank's Data Methods forum also related to the same paper cited above: "Observed Power" and other "Power" Issues https://discourse.datamethods.org/t/observed-power-and-other-power-issues/731/30 2. If you are still compelled (voluntarily or involuntarily), you may want to review the vignette for the longpower package which may have some insights, and/or contact the package maintainer for additional guidance on how to structure the code. See the vignette here: https://cran.r-project.org/web/packages/longpower/vignettes/longpower.pdf 3. Don't calculate post hoc power. Regards, Marc Schwartz ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
