[R] ANOVA/ANCOVA Repeated Measure Mixed Model

Nick GH ghv202 at nyu.edu
Fri Oct 7 05:33:11 CEST 2011


Hello,

I am trying to test some results I have for significance. It has been
recommended that I use R and I am completely new to this.

Set-up:

   Groups: two groups of 8 subjects (16 total)
   Two conditions: alert and passive
   Measurements: responses for three different stimuli (A, B, and C)
measured in each condition

Experiment: Testing the order of conditions 

   Group one: Alert A, B and C followed by Passive A, B, and C 
   Group two: Passive A, B, and C followed by Alert A, B, and C

Stimuli A, B and C are randomly interleaved in the experiment, does this
matter in my ANOVA?
 
I am interested in making a between and within group comparison of responses
to A, B, and C

<he>Here is what I am doing:


My data is arranged in the following way

Group Subject Condition Stimulus Response
One      S1          Alert          A       _Value_
One      S1          Alert          B       _Value_
One      S1          Alert          C       _Value_
One      S1          Passive      A       _Value_
One      S1          Passive      B       _Value_
One      S1          Passive      C       _Value_
One      S2          Alert          A       _Value_
...

Two      S9          Alert          A       _Value_
Two      S9          Alert          B       _Value_
Two      S9          Alert          C       _Value_
...

This is the code I used:

M400_500_anova = aov(Response ~ Condition * Stimulus * Group +
Error(Subject/Condition * Stimulus ), data=My_Data)

Is this correct?

ANCOVA question


I haven't gotten as far with this one, but I want to do an ANCOVA using the
passive responses as a co-variate, but I am not sure how to even do this
with so many factors/groups/repeated measures. I am also not sure what
function to use in R, or how to even write the command. 

Thank you so much for your help!
Nick GH

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