You have confused 'Anova', 'aov' and 'anova'. R has aov() and
anova(), package car (called from Rcmdr) has Anova(). They are not
the same things: Anova computes (so-called, by SAS) 'type-II or
type-III analysis-of-variance tables', something deliberately not
available in base R.
See http://www.stats.ox.ac.uk/pub/MASS3/Exegeses.pdf for some
background and why many distinguished statisticians regard your
example of the use of Anova() as meaningless.
In any case, lm (in your subject line) is innocent ... it does not
compute any form of ANOVA table.
On Tue, 31 Aug 2010, Iasonas Lamprianou wrote:
Dear all
I have found that the two "equivalent" commands do not produce the same results.
1. (I wrote this command by hand, this is what I would do usually)
>summary(aov(eduyrs ~ cntry * edf, data=ESS1))
Df Sum Sq Mean Sq F value Pr(>F)
cntry 1 257 256.65 21.2251 4.243e-06 ***
edf 4 11010 2752.42 227.6296 < 2.2e-16 ***
cntry:edf 4 24 6.03 0.4987 0.7367
Residuals 3205 38754 12.09
---
Signif. codes: 0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1
2. (I run this from Rcmdr, this is what my students would normally do)
>AnovaModel.2 <- (lm(eduyrs ~ cntry*edf, data=ESS1))
> Anova(AnovaModel.2)
Anova Table (Type II tests)
Response: eduyrs
Sum Sq Df F value Pr(>F)
cntry 38 1 3.1158 0.07763 .
edf 11010 4 227.6296 < 2e-16 ***
cntry:edf 24 4 0.4987 0.73672
Residuals 38754 3205
---
Signif. codes: 0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1
Unfortunately, the results are different. Could anyone, please, explain why?
Dr. Iasonas Lamprianou
Assistant Professor (Educational Research and Evaluation)
Department of Education Sciences
European University-Cyprus
P.O. Box 22006
1516 Nicosia
Cyprus
Tel.: +357-22-713178
Fax: +357-22-590539
Honorary Research Fellow
Department of Education
The University of Manchester
Oxford Road, Manchester M13 9PL, UK
Tel. 0044 161 275 3485
iasonas.lampria...@manchester.ac.uk
--
Brian D. Ripley, rip...@stats.ox.ac.uk
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
1 South Parks Road, +44 1865 272866 (PA)
Oxford OX1 3TG, UK Fax: +44 1865 272595
______________________________________________
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.
