[R] inquiry about anova and ancova

Andrew Robinson A.Robinson at ms.unimelb.edu.au
Wed Jul 11 12:29:41 CEST 2007

Hi Mary,

it sounds like you have a split-plot design, or more gruesomely, a
split-subject design.  

The model that I infer from your description of the design can be fit
using the lme() function of the nlme() package, along the lines of a
similar analysis documented in section 1.6 of Pinheiro and Bates
(2000).  It should also be possible by using the aov() function in
base R.



On Wed, Jul 11, 2007 at 10:50:57AM +0100, Anderson, Mary-Jane wrote:
> Dear R users,
> 	 I have a rather knotty analysis problem and I was hoping that
> someone on this list would be able to help. I was advised to try this list
> by a colleague who uses R but it is a statistical inquiry not about how to
> use R.
>  In brief I have a 3x2 anova, 2 tasks under 3 conditions, within subjects. I
> also took a variety of personality measures that might influence the results
> under the different conditions. I had thought that an ancova would be the
> best test, but it might be the case that this would not work with a within
> subjects design. I have not found anything that explicitly states whether or
> not it would, but all the examples I have read are between subjects design.
>  I also thought of investigating a manova, but it is not really the case
> that I have more than one DV, it is the same DV in 6 different combinations
> of task and condition. 
>  There were 4 personality measures and I wanted to look at the degree to
> which they affected the task/ condition interaction. 
>  I have explained this briefly here, but I can of course provied more
> details to anyone who can advise me further with this.
> Thanks,
> Mary-Jane Anderson 
> Information Analyst 
> Platform Project
> Information Services Division, 
> NHS National Services Scotland, 
> Gyle Square, 
> 1 South Gyle Crescent, 
> Edinburgh, 
> EH12 9EB. 
> 0131 275 7163.
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Andrew Robinson  
Department of Mathematics and Statistics            Tel: +61-3-8344-9763
University of Melbourne, VIC 3010 Australia         Fax: +61-3-8344-4599

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