Re: [R] Asking, are simple effects different from 0

2008-03-06 Thread jebyrnes
Ah, I see where we are talking past each other. In my particular analysis (I'm looking at deviations from a predicted value), any deviation from 0 (whether due to grand mean or not) is actually very very interesting. What is ultimately interesting to me is the sign of that difference, but, I nee

Re: [R] Asking, are simple effects different from 0

2008-03-06 Thread Chuck Cleland
On 3/5/2008 3:19 PM, jebyrnes wrote: > Indeed, but are not each of the cell means also evaluations of the effect of > one factor at the specific level of another factor? Is this an issue of > "Tomato, tomahto". I don't think it is "tomato, tomahto". Say the grand mean is around 100 and the w

Re: [R] Asking, are simple effects different from 0

2008-03-05 Thread jebyrnes
Indeed, but are not each of the cell means also evaluations of the effect of one factor at the specific level of another factor? Is this an issue of "Tomato, tomahto". I guess my question is, if I want to know if each of those is different from 0, then should I use the 48df from the full model,

Re: [R] Asking, are simple effects different from 0

2008-03-05 Thread Chuck Cleland
On 3/5/2008 1:32 PM, jebyrnes wrote: > Ah. I see. So, if I want to test to see whether each simple effect is > different from 0, I would do something like the following: > > cm2 <- rbind( > "A:L" = c(1, 0, 0, 0, 0, 0), > "A:M" = c(1, 1, 0, 0, 0, 0), > "A:H" = c(1, 0, 1, 0, 0, 0), > "B:L" =

Re: [R] Asking, are simple effects different from 0

2008-03-05 Thread jebyrnes
Ah. I see. So, if I want to test to see whether each simple effect is different from 0, I would do something like the following: cm2 <- rbind( "A:L" = c(1, 0, 0, 0, 0, 0), "A:M" = c(1, 1, 0, 0, 0, 0), "A:H" = c(1, 0, 1, 0, 0, 0), "B:L" = c(1, 0, 0, 1, 0, 0), "B:M" = c(1, 1, 0, 1, 1, 0)

Re: [R] Asking, are simple effects different from 0

2008-03-05 Thread Chuck Cleland
On 3/5/2008 10:09 AM, jebyrnes wrote: > Huh. Very interesting. I haven't really worked with manipulating contrast > matrices before, save to do a prior contrasts. Could you explain the matrix > you laid out just a bit more so that I can generalize it to my case? Each column corresponds to

Re: [R] Asking, are simple effects different from 0

2008-03-05 Thread jebyrnes
Huh. Very interesting. I haven't really worked with manipulating contrast matrices before, save to do a prior contrasts. Could you explain the matrix you laid out just a bit more so that I can generalize it to my case? Chuck Cleland wrote: > > >One approach would be to use glht() in t

Re: [R] Asking, are simple effects different from 0

2008-03-05 Thread Chuck Cleland
On 3/4/2008 2:45 PM, Jarrett Byrnes wrote: > Hello, R-i-zens. I'm working on an data set with a factorial ANOVA > that has a significant interaction. I'm interested in seeing whether > the simple effects are different from 0, and I'm pondering how to do > this. So, I have > > my.anova<-lm

[R] Asking, are simple effects different from 0

2008-03-04 Thread Jarrett Byrnes
Hello, R-i-zens. I'm working on an data set with a factorial ANOVA that has a significant interaction. I'm interested in seeing whether the simple effects are different from 0, and I'm pondering how to do this. So, I have my.anova<-lm(response ~ trtA*trtB) The output for which gives me a