[R] anovas ss typeI vs typeIII

[Helios de Rosario]

Hi, you should give more details of your problem (at least some output,
as Peter Daalgard says). But you are probably asking for something like
this:
http://www.r-bloggers.com/anova-%E2%80%93-type-iiiiii-ss-explained/
or many other webpages that you may find if you Google or R-seek with
keywords like "anova" "type i", "type iii", etc.

If you have within-subjects factors, the same commands will not give
you a sensible result. If you want to use Anova() for that, you should
use the arguments "idata", "idesign", etc., as explained in the help
page of that function, or in the web appendix to the "CAR" book:
http://socserv.mcmaster.ca/jfox/Books/Companion/appendix/Appendix-Multivariate-Linear-Models.pdf

Helios De Rosario



-- 
Helios de Rosario Martínez
 
 Researcher


>>> El día 20/05/2012 a las 0:58, jacaranda tree
<myjacaranda at yahoo.com> escribió:
> Hi all,
> I have been struggling with ANOVAs on R. I am new to R, so I created
a 
> simple data frame, and I do some analyses on R just to learn R and
then check 
> them on SPSS to make sure that I am doing fine. Here is the problem
that I've 
> run into:
> 
> when we use the aov function, it uses SS Type I as default (on SPSS
it is 
> Type III). Then I used the Anova function under cars package using
the 
> command:
> 
> mod <- lm(DV
> ~ IV1*IV2, data = mydata,
> contrasts=list(IV1=contr.sum,
> IV2=contr.sum))
> Anova(mod, type=”3”)
> 
> Above, both of my IVs are between-SS variables. But still, results
from this 
> model do not match the results from SPSS (I have to say they are not
too 
> different either). But I was wondering if I am doing something wrong.
If what 
> I am doing is okay, then my next question is can I use the same set
of 
> commands (for Anova function) if one of my IVs was within-SS and the
other IV 
> was between-SS? 
> 
> 
> Thank you very much!


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