For power studies you need to think about what the data will look like under the alternative hypothesis. Is the data shifted over a certain amount? (the most common assumption), or scaled? Or both? Or a completely different shape? Etc.
My preferred method for power studies in this case is to use simulation: 1. decide what you data is likely to look like (based on previous data, assumptions, ...) 2. decide how you will analyze the data (possibly iterate between 1 and 2) 3. write a function that simulates data under the alternative hypothesis, then analyzes it (using decisions from 1 and 2) and returns the p-value or test statistic. The function will often have a parameter for sample size and a parameter for the size of the difference (scale, etc.). 4. use the replicate function to run your function a bunch of times. 5. the proportion of times that the above gives significant results is an estimate of the power. Hope this helps, -- Gregory (Greg) L. Snow Ph.D. Statistical Data Center Intermountain Healthcare greg.s...@imail.org 801.408.8111 > -----Original Message----- > From: r-help-boun...@r-project.org [mailto:r-help-boun...@r- > project.org] On Behalf Of Alon Ben-Ari > Sent: Tuesday, September 22, 2009 9:35 AM > To: r-help@r-project.org > Subject: [R] No parametric methods > > Hello I am interested in finding out a method of power analysis > (effect > size and sample size calculation ) using R in non parametric methods? > > I am running R 2.8.1 running on linux open SUSE > > Any libraries or documentation , I was not bale to google up any. > > Thanks in Advance, > > Ben-Ari Alon, MD > University of Pittsburgh. > > [[alternative HTML version deleted]] > > ______________________________________________ > R-help@r-project.org mailing list > 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. ______________________________________________ R-help@r-project.org mailing list 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.
