Hi, Thank you very much for the answer.
However, I have still some misunderstandings. from the output, can we say that plant and leaf age are significant but not their interaction? And the last question I promise, what would you advise me to write in the paper to explain the different method and ackonwledge for the df? Thank you again, julien. Frank E Harrell Jr wrote: > > pompon wrote: >> Hello, >> >> I am a beginner in R and statistics, so my question may be trivial. Sorry >> in >> advance. >> I performed a Cox proportion hazard regression with 2 categorical >> variables >> with cph{design}. Then an anova on the results. >> the output is >> >>> anova(cph(surv(survival, censor) ~ plant + leaf.age + plant*leaf.age, >>> Mpnymph) >> >> Wald Statistics Response: Surv(survival, >> censored) >> >> Factor Chi-Square >> d.f. P >> plant (Factor+Higher Order Factors) 96.96 12 <.0001 >> All Interactions 10.58 >> 6 0.1022 >> leaf.age (Factor+Higher Order Factors) 29.11 7 0.0001 >> All Interactions 10.58 >> 6 0.1022 >> plant * leaf.age (Factor+Higher Order Factors) 10.58 6 0.1022 >> TOTAL 106.63 13 <.0001 >> >> What do "All interaction" stand for? >> The real df of for plant is 6 and 1 for leaf.age. Then, which chi square >> is >> one for my main factors anf their interaction. >> >> thank you, >> Julien. > > Julien, > > I know what you mean when you say 'real df' but that's not the whole > story as plant has 6 more df by interacting with a single df variable. > There is no such thing as 'the' main effect test for plant. The 12 df > test is unique and tests whether plant is associated with Y for any > level of leaf.age. > > You can see exactly what is being tested by using various print options > for anova.Design, as described in the help file. The "dots" option is > easy on the eyes. > > Frank > -- > Frank E Harrell Jr Professor and Chair School of Medicine > Department of Biostatistics Vanderbilt University > > ______________________________________________ > 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. > > -- View this message in context: http://www.nabble.com/anova%28cph%28..%29-output-tp23563818p23617483.html Sent from the R help mailing list archive at Nabble.com. ______________________________________________ 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.