?power.anova.test is designed for 1 way models. I would be intrigued to found out more about power in complicated designs. Do look into the archives at http://finzi.psych.upenn.edu/search.html In the past, I used power.t.test on individual model coefficients, though I am not sure it was correct. Hank Stevens
On Oct 18, 2005, at 3:50 PM, Chris Behr wrote: > Hello, > > I am a new user of R and trying to assess the sample size for data > that is > being collected on water quality at sites across a wide geographic > region. A > preliminary set of data has been collected and I would like to use > it to > assess whether we are collecting enough data and in the right places. > > A factorial approach was initially used to characterize sites by > well type, > latrine type, distance between well and latrine, and ecological > region. > Altogether the basic structure has: > > 3 types of wells > 3 types of latrines > 4 distance categories > 13 regions > > We define a “site-type” as: a well-latrine-distance combination. > There are > 36 of these. A number of replicates (between 1 and 4) of the 36 > site-types > are included in the set of sites in each of the 13 regions. Some > regions > have more replicates than others due to complexity in the region. > In total > there are 936 sites. > > At this point, I have an ANOVA model with water quality measures > and only > (these) categorical data. I want to know if I am collecting enough > samples > (given alpha and beta levels) to see if there are effects for wells, > latrines, distances, and region (independently), as well as > interactions for > well-distance, well-latrine, and well-region. I would like to also > perform a > power analysis to allow the power vary with sample size. > > I am working my way through various texts and help functions but > thought I > would see if anyone else has learned how to do this already. > > I would appreciate any and all guidance. > > Best wishes, Chris > > Christopher Behr > Principal Analyst > > eDesign Dynamics > www.edesigndynamics.com > Christopher Behr > Principal Analyst > > eDesign Dynamics > www.edesigndynamics.com > > 4024 Calvert St. NW > Washington DC 20007 > (202) 298-6437 (t/f) > (551) 998-4823 (c) > > ______________________________________________ > [email protected] mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide! http://www.R-project.org/posting- > guide.html > Dr. Martin Henry H. Stevens, Assistant Professor 338 Pearson Hall Botany Department Miami University Oxford, OH 45056 Office: (513) 529-4206 Lab: (513) 529-4262 FAX: (513) 529-4243 http://www.cas.muohio.edu/~stevenmh/ http://www.muohio.edu/ecology/ http://www.muohio.edu/botany/ "E Pluribus Unum" ______________________________________________ [email protected] mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
