Re: [R] Brown-Forsythe test of equality of MEANS

[Iasonas Lamprianou]

Thank you for replying. But there is another test with the same name which 
tests for equality of means. It is a robust version of ANOVA, like the Welch 
(ANOVA) test. They are both available at SPSS. the Welch test is available 
through the oneway.test in R but the Brown-Forsythe test for the equality of 
means is not. You may have a look at 
        
        
De
Beuckelaer, A. (1996). A closer examination on some parametric
alternatives to the ANOVA F test. Statistical Papers, 37, 291-305 if you like 
to see what I mean. 
But thank you for replying so soon. I hope that somebody else solved this 
issue. Also, by the way, I have a second question, if anyone can help. I am 
looking for an R package to run a Dunnett's T3 or C test for Post Hoc 
comparisons when we 'suffer' from heteroscedasticity. (Even Games-Howell would 
do if the Dunnett's tests are not available )

Thank you again for your help. 




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

--- On Mon, 30/8/10, Bert Gunter <gunter.ber...@gene.com> wrote:

From: Bert Gunter <gunter.ber...@gene.com>
Subject: Re: [R] Brown-Forsythe test of equality of MEANS
To: "Iasonas Lamprianou" <lampria...@yahoo.com>
Cc: r-help@r-project.org
Date: Monday, 30 August, 2010, 21:25

Inline below.
 
-- Bert


On Mon, Aug 30, 2010 at 1:05 PM, Iasonas Lamprianou <lampria...@yahoo.com> 
wrote:


Dear friends,
two years ago (as I found on the web) Paul sent the following message but I was 
not able to find if he got an answer. Today I have the same question and it 
would be great if I could find out that this test has been implemented 
(somehow) in R. Please do not confuse it with the Brown-Forsythe test of 
equality of variances. Thank you:


I've been searching around for a function for computing the Brown-Forsythe F* 
statistic which is a substitute for the normal ANOVA F statistic for when there 
are unequal variances, and when there is evidence of non-normality.

 
False, I think, as I'm not entirely clear on your meaning. Brown-Fosythe is a 
test for the equality of spreads among groups. From Wikipedia:
 

The transformed response variable is constructed to measure the spread in each 
group. Let


 
where  is the median of group j. The Brown–Forsythe test statistic is the 
model F statistic from a one way ANOVA on zij:

In particular, it is NOT " a substitute for the normal ANOVA F statistic for 
when there are unequal variances, and when there is evidence of non-normality."
--
Bert Gunter
Genentech Noclinical Statistics
 



      
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