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  1. How do you carry out analysis of covariance using R?
  2. How do you interpret the results?
  3. A practical example will be highly appreciated.
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2 Answers 2

Here is a detailed presentation

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Lamentably, in that document Crawley perpetuates the myth that ANCOVA can be applied to scenarios when the covariate is correlated with an IV, even when this explicitly violates an assumption of ANCOVA. –  Mike Lawrence Feb 11 '11 at 13:20
    
thanks for the document. i will take a close look at it. –  Jones Feb 14 '11 at 5:12
    
ancova makes no such assumption. your statement is tantamount to saying multiple regression is only valid with uncorrelated predictors, which is not true. –  user5620 Aug 1 '11 at 0:20
    
"No such assumption" refers to what? –  whuber Aug 1 '11 at 2:26
    
Would you be able to summarize this presentation here? –  whuber Aug 1 '11 at 2:27

This is a very clear presentation from a biologist:

R in Ecology & Evolution: Comparing two regression slopes by means of an ANCOVA

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