From tlogvinenko at partners.org  Thu Jul 29 22:43:20 2004
From: tlogvinenko at partners.org (tlogvinenko@partners.org)
Date: Thu Jul 29 22:43:22 2004
Subject: [Rd] aov for unbalanced design (PR#7144)
Message-ID: <20040729204320.05FE5FC04@slim.kubism.ku.dk>

Full_Name: Tanya Logvinenko
Version: 1.7.0
OS: Windows 2000
Submission from: (NULL) (132.183.156.125)


For unbalanced design, I ran into problem with ANOVA (aov function). The sum of
squares for only for the second factor and total are computed correctly, but sum
of squares for the first factor is computed incorreclty. Changing order of
factors in the formula changes the ANOVA table. For the balanced design, there
is no such problem.

> summary(aov(data[1,]~factor1+factor2))
            Df  Sum Sq Mean Sq F value    Pr(>F)    
factor1      5 1524420  304884  6.4529 0.0003229 ***
factor2      7 1447830  206833  4.3776 0.0017808 ** 
Residuals   31 1464674   47248                      
---
Signif. codes:  0 `***' 0.001 `**' 0.01 `*' 0.05 `.' 0.1 ` ' 1 
> summary(aov(data[1,]~factor2+factor1))
            Df  Sum Sq Mean Sq F value    Pr(>F)    
factor2      7 1648225  235461  4.9836 0.0007295 ***
factor1      5 1324025  264805  5.6046 0.0008612 ***
Residuals   31 1464674   47248                      
---
Signif. codes:  0 `***' 0.001 `**' 0.01 `*' 0.05 `.' 0.1 ` ' 1


[Rd] aov for unbalanced design (PR#7144)
tlogvinenko@partners.org