On Feb 14, 2012, at 5:36 PM, Xiang Gao wrote:
Hi I am working on a Nested one-way ANOVA. I don't know how to implement R code to test the significance of the random factor
Have you read what the unofficial Mixed Model FAQ says about testing for significance on random effects?
http://glmm.wikidot.com/faq
My R code so far can only test the fixed factor :
That may be the intent of the authors. They may want to make it sufficiently difficult so that an adequate barrier prevents the unwary from taking some "easy way out". You probably need to describe your study (assuming this is not an assigned homework exercise) in sufficient scientific detail and do so on the mixed-models mailing list.
-- David.
anova(lme(PCB~Area,random=~1|Sites, data = PCBdata)) numDF denDF F-value p-value (Intercept) 1 12 1841.7845 <.0001 Area 1 4 4.9846 0.0894 Here is my data and my hand calculation.PCBdataArea Sites PCB 1 A 1 18 2 A 1 16 3 A 1 16 4 A 2 19 5 A 2 20 6 A 2 19 7 A 3 18 8 A 3 18 9 A 3 20 10 B 4 21 11 B 4 20 12 B 4 18 13 B 5 19 14 B 5 20 15 B 5 21 16 B 6 19 17 B 6 23 18 B 6 21 By hand calculation, the result should be: Source SS DF MS Areas 18.00 1 18.00 Sites 14.44 4 3.61 Error 20.67 12 1.72 Total 53.11 17 --- MSareas/MSsites = 4.99 --- matching the R output MSsites/MSE = 2.10 Conclusion is that Neither of Areas nor Sites make differences. My R code so far can only test the fixed effect : anova(lme(PCB~Area,random=~1|Sites, data = PCBdata)) numDF denDF F-value p-value (Intercept) 1 12 1841.7845 <.0001 Area 1 4 4.9846 0.0894 -- Xiang Gao, Ph.D. Department of Biology University of North Texas ______________________________________________ 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.
David Winsemius, MD West Hartford, CT ______________________________________________ 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.
