Dear helpers,
I have a 2x2 mixed design with two "groups" (between-subjects) and two
presentation-types (within-subjects).
The difference between groups is in the order of manipulations:
group.CD having first a block of present.type.C and then a block of
present.type.D, each block containing 31 trials.
group.DC having first a block of present.type.D and then a block of
present.type.C, each block containing 31 trials.
I'm mostly interested in the interaction group:present.type - to see if the
order of presentation has an influence on performance time (the dependent
measure).
The fundamental ANOVA model is:
>aov(t.total~group*present.type+Error(subj/present.type), data=dat2)
Unfortunately, the standard deviations of the different interaction-cells
differ markedly (~20, ~9, ~9, ~18) so it seems that a correction for
departure from sphericity is appropriate.
I'm trying to achieve that using the Anova function from the car package,
but fail to understand what should be the model, the idata and idesign
parameter (which seem to be required for a repeated-measures analysis
design).
I'd appreciate any help with getting the right required model and parameters
(idata, idesign and icontrasts).
Thanks,
dror
--------------------
My data set is stored in a data.frame with the following columns:
> names(dat2)
[1] "t.total" "t.err" "trial.num" "subj"
"present.type"
[6] "ord" "group" "dat.name"
and the only table of results I'm getting is:
> summary(Anova(m.tmp))
Sum Sq Df F value Pr(>F)
Min. : 17810 Min. : 1.0 Min. :69.01 Min. :1.278e-15
1st Qu.: 41232 1st Qu.:108.8 1st Qu.:69.01 1st Qu.:1.278e-15
Median : 64654 Median :216.5 Median :69.01 Median :1.278e-15
Mean : 64654 Mean :216.5 Mean :69.01 Mean :1.278e-15
3rd Qu.: 88075 3rd Qu.:324.2 3rd Qu.:69.01 3rd Qu.:1.278e-15
Max. :111497 Max. :432.0 Max. :69.01 Max. :1.278e-15
NA's : 1.00 NA's :1.000e+00
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