[R] Two Different Interaction Terms for Mixed Factorial ANOVA in R?

[Angela Radulescu]

I have the following R output from a mixed factorial ANOVA:

Error: subj
                 Df Sum Sq Mean Sq F value  Pr(>F)   group
1   11.3   11.26   0.449 0.50811
singleType        1    0.7    0.66   0.026 0.87220   group:singleType
1  237.5  237.53   9.484 0.00461 **Residuals        28  701.3   25.04
                 ---Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05
‘.’ 0.1 ‘ ’ 1
Error: subj:singleType
                 Df Sum Sq Mean Sq F value Pr(>F)
singleType        1 1566.4  1566.4 411.445 <2e-16 ***group:singleType
1    3.4     3.4   0.893  0.352    Residuals        30  114.2     3.8
                 ---Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05
‘.’ 0.1 ‘ ’ 1
Error: Within
            Df Sum Sq Mean Sq F value Pr(>F)Residuals 3286   5747   1.749

Here "group" is the between factor (2 levels) and "singleType" the within
factor (2 levels). I'm not sure why there are two group:singleType
interaction terms. Any help would be much appreciated!

For reference, here is the original aov call:

anova.p = aov(data = dat.colSingle, rt ~ (group*singleType) +
Error(subj/singleType))
summary(anova.p)

Thank you!

-- 
Angela Radulescu

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