[R] Post hoc analysis for ANOVA with repeated measures

[David Winsemius]

My suggestion is that you take the weekend lull in readership to now  
read the Posting Guide which it appears you nave not yet done. Had you  
done so you should have encountered the advice about how to  
successfully attach data files. (None came through.) You would also  
have read the request that before posting that you search the R-help  
archives for previous questions that match yours. (There are several  
using the search terms "post-hoc repeated measures":

http://search.r-project.org/cgi-bin/namazu.cgi?query=post-hoc+repeated+measures&max=100&result=normal&sort=score&idxname=functions&idxname=Rhelp08&idxname=Rhelp10&idxname=Rhelp02

-- 
David.
On Jan 9, 2011, at 7:10 AM, Frodo Jedi wrote:

> Dear all,
> how can I perform a post hoc analysis for ANOVA with repeated  
> measures (in
> presence of a balanced design)?
> I am not able to find a good example over internet in R...is there  
> among you
> someone so kind to give
> me an hint with a R example please?
>
> For example, the aov result of my analysis says that there is a  
> statistical
> difference between stimuli (there are 7 different stimuli).
> ...I would like to know which stimuli are involved.
>
>> aov1 = aov(response ~ stimulus*condition + Error(subject/ 
>> (stimulus*condition)),
>> data=scrd)
>> summary(aov1)
>
> Error: subject
>          Df Sum Sq Mean Sq F value Pr(>F)
> Residuals 14 227.57  16.255
>
> Error: subject:stimulus
>          Df Sum Sq Mean Sq F value  Pr(>F)
> stimulus   6 11.695 1.94921  2.3009 0.04179 *
> Residuals 84 71.162 0.84717
> ---
> Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1
>
> Error: subject:condition
>          Df Sum Sq Mean Sq F value   Pr(>F)
> condition  1 42.076  42.076  12.403 0.003386 **
> Residuals 14 47.495   3.393
> ---
> Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1
>
> Error: subject:stimulus:condition
>                   Df Sum Sq Mean Sq F value Pr(>F)
> stimulus:condition  6  9.124  1.5206  1.4465 0.2068
> Residuals          84 88.305  1.0513
>>
>
>
>
> In attachment you find the table I am using, you can access it by  
> means of:
> scrd<-
> read.csv(file='/Users/....../tables_for_R/ 
> table_quality_gravel.csv',sep=',',header=T)
>
>
> The data are from an experiment where participants had to evaluate  
> on a seven
> point likert scale
> the realism of some stimuli, which are presented both in condition  
> "A" and in
> condition "AH".
>
>
> Thanks in advance
>
> Best regards
>
>
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> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.

David Winsemius, MD
West Hartford, CT