I continue to be surprised that the majority of users do not search the
help archives linked from www.r-project.org. This is a much discussed
topic, including vast amounts of information on the silliness of type
III tests.
Frank
Ravi Kulkarni wrote:
Hello,
I believe the aov() function in R uses a "Type-I sum-of-squares" by
default as against "Type-III".
This is relevant for me because I am trying to understand ANOVA in R using
my knowledge of ANOVA in SPSS. I can only reproduce the results of an ANOVA
done using R through SPSS if I specify that SPSS uses a Type-I
sum-of-squares. (And yes, I know that when the sample sizes of all groups
are equal, Type-I and Type-III produce the same answers.)
My questions: 1) exactly what is the difference between the two types of
sums-of-squares?
2) how can I make R use a Type-III s-o-s? Should I? R
must have some reason for using Type-I as default rather than Type-III.
(Given a choice, believe R!)
A reference (stats book, URL...) would be helpful...
Ravi
--
Frank E Harrell Jr Professor and Chairman 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.
