[R] Repeated Measure different results to spss

[John Vokey]

This should work (with x containing the dataframe):

 > x$Id=factor(x$Id)
 > x$Group=factor(x$Group)
 > x$Task=factor(x$Task)
 > str(x)
'data.frame':	48 obs. of  4 variables:
$ Id   : Factor w/ 24 levels "1","2","3","4",..: 1 2 3 4 5 6 7 8 9  
10 ...
$ Group: Factor w/ 2 levels "1","2": 1 1 1 1 1 1 1 1 1 1 ...
$ Task : Factor w/ 2 levels "1","2": 1 1 1 1 1 1 1 1 1 1 ...
$ Score: num  0.39 0.48 0.59 0.33 0.38 0.37 0.47 0.2 0.29 0.41 ...
 > out.aov = aov(Score~Group*Task+Error(Id+Id:Task),data=x)
 > summary(out.aov)

Error: Id
           Df  Sum Sq Mean Sq F value Pr(>F)
Group      1 0.03420 0.03420  2.1382 0.1578
Residuals 22 0.35189 0.01600

Error: Id:Task
            Df   Sum Sq  Mean Sq F value  Pr(>F)
Task        1 0.048133 0.048133  5.2144 0.03242 *
Group:Task  1 0.024687 0.024687  2.6743 0.11621
Residuals  22 0.203080 0.009231
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1
 >

out.aov = aov(Score~Group*Task+Error(Id),data=x) will work as well,  
but the error-term will be labelled simply as ``Within'', rather than  
as the interaction of Id*Task

>
> Hi,
>
> I have some problems with my repeated measures analysis. When I  
> compute it
> with SPSS I get different results than with R. Probably I am doing  
> something
> wrong in R.
> I have two groups (1,2) both having to solve a task under two  
> conditions
> (1,2). That is one between subject factor (group) and one within  
> subject
> factor (task). I tried the following:
>
>  aov(Score ~factor(Group)*factor(Task)+Error(Id)))
>  aov(Score ~factor(Group)*factor(Task))
> but it leads to different results than my spss. I definitely miss  
> some point
> here .
>
> Thanks for you help.
>
> Id	Group	Task	Score
> 1	1	1	0.39
> 2	1	1	0.48