Meesters, Erik wrote: > Dear people, > I've a problem in doing a power calculation. In Fryer and Nicholson > (1993), ICES J. mar. Sci. 50: 161-168 page 164 an example is given with > the following characteristics > T=5, points in time > R=5, replicates > Var.within=0.1 > q=10, a 10% increase per year > The degrees of freedom for the test are calculated as Vl=T*R-2=23 and > the non-centrality parameter Dl=4.54. > Using this they get a power of 0.53, but the result that I'm getting is > 0.05472242. > > I've tried this several ways in R, but I'm not able to come up with the > same number. Am I doing something wrong in the calculation of the power? > Here's my code: > > T<-5 > R<-5 > sigmasq<-0.1 > q<-10 > Vl<-(T*R)-2 > Dl<-(R*(T-1)*T*(T+1)/(12*sigmasq))*(log(1+(q/100)))^2 #Dl result is > still similar > > power.1<-1-pf(qf(.95,(T*R-2),1,ncp=0),(T*R-2),1,ncp=Dl) > > Thank you for any suggestions/help. > I think your DF are upside-down:
> power.1<-1-pf(qf(.95,1,(T*R-2),ncp=0),1,(T*R-2),ncp=Dl) > power.1 [1] 0.532651 -- O__ ---- Peter Dalgaard Ă˜ster Farimagsgade 5, Entr.B c/ /'_ --- Dept. of Biostatistics PO Box 2099, 1014 Cph. K (*) \(*) -- University of Copenhagen Denmark Ph: (+45) 35327918 ~~~~~~~~~~ - ([EMAIL PROTECTED]) FAX: (+45) 35327907 ______________________________________________ R-help@stat.math.ethz.ch 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.